Bluetooth
Bluetooth
1 Take a look around
Look around you at the moment, you have your keyboard connected to the computer, as well as a printer, mouse, monitor and so on. What (literally) joins all of these together?, they are connected by cables. Cables have become the bane of many offices, homes etc. Most of us have experienced the 'joys' of trying to figure out what cable goes where, and getting tangled up in the details. Bluetooth essentially aims to fix this, it is a cable-replacement technology
2 How?
Conceived initially by Ericsson, before being adopted by a myriad of other companies, Bluetooth is a standard for a small , cheap radio chip to be plugged into computers, printers, mobile phones, etc.A Bluetooth chip is designed to replace cables by taking the information normally carried by the cable, and transmitting it at a special frequency to a receiver Bluetooth chip, which will then give the information received to the computer, phone whatever.
3 How about ?
That was the original idea, but the originators of the original idea soon realised that a lot more was possible. If you can transmit information between a computer and a printer, why not transmit data from a mobile phone to a printer, or even a printer to a printer?. The projected low cost of a Bluetooth chip (~$5), and its low power consumption, means you could literally place one anywhere.
4 Ideas, ideas...
With this viewpoint interest in Bluetooth is soaring, lots of ideas are constantly emerging, some practical and feasible e.g.: Bluetooth chips in freight containers to identify cargo when a lorry drives into a storage depot, or a headset that communicates with a mobile phone in your pocket, or even in the other room, other ideas not so feasible: Refrigerator communicating with your Bluetooth-enabled computer, informing it that food supply is low, and to inform the retailer over the internet.
5 The future, this website
Whatever the ideas, Bluetooth is set to take off. To be honest it's going to be forced down the consumers necks, whether they want it or not, as too many companies have invested in it. This website is generally geared towards the technical issues surrounding Bluetooth, and its implementation in real life. But free feel to have a look around anyway, and see why this technology will have such a big impact on our lives. If you're a complete beginner & you want to know more go to the other pages on the website: the Tutorial has a reasonably in-depth guide to Bluetooth (can be quite technical in parts though), our members-only Download** page has some more general introductions to Bluetooth to download. Also check out the Resource Center, Articles, Glossary & Knowledge Base to further enhance your Bluetooth education. There are also related Resource Centers on IEEE 802.11 WiFi Wireless LANs, HomeRF, GPS, SyncML, ZigBee and other mobile and wireless technologies. Enjoy!
** Note that although many sections of this web site are freely available, some require a free membership and others are available only to paid members.
6 Looking after your teeth
By the way if, you're wondering where the Bluetooth name originally came from, it named after a Danish Viking and King, Harald Blåtand (translated as Bluetooth in English), who lived in the latter part of the 10th century. Harald Blåtand united and controlled Denmark and Norway (hence the inspiration on the name: uniting devices through Bluetooth). He got his name from his very dark hair which was unusual for Vikings, Blåtand means dark complexion. However a more popular, (but less likely reason), was that Old Harald had a inclination towards eating Blueberries , so much so his teeth became stained with the colour, leaving Harald with a rather unique set of molars. And you thought your teeth were bad...
Voice Morphing
Voice Morphing
Voice Morphing which is also referred to as voice transformation and voice conversion is a technique to modify a source speaker's speech utterance to sound as if it was spoken by a target speaker. There are many applications which may benefit from this sort of technology. For example, a TTS system with voice morphing technology integrated can produce many different voices. In cases where the speaker identity plays a key role, such as dubbing movies and TV-shows, the availability of high quality voice morphing technology will be very valuable allowing the appropriate voice to be generated (maybe in different languages) without the original actors being present.
There are basically three inter-dependent issues that must be solved before building a voice morphing system. Firstly, it is important to develop a mathematical model to represent the speech signal so that the synthetic speech can be regenerated and prosody can be manipulated without artifacts. Secondly, the various acoustic cues which enable humans to identify speakers must be identified and extracted. Thirdly, the type of conversion function and the method of training and applying the conversion function must be decided.
The aim of this research is to develop flexible high quality algorithms which can morph speech from one speaker. A system has been developed based on a pitch synchronous sinusoidal model which uses LSF feature encoding and linear transforms. To ensure high quality, a number of novel techniques have been developed to minimise the artifacts which typically result from loss of glottal source information, formant bandwidth broadening, phase incoherance and spectral colouring of unvoiced sounds. Full details are given in references [1] and [2] and some demonstration files are given below.
Current work is focussed on extending the techniques to allow the conversion of an unknown speaker's voice to sound like that of a known target speaker.
Demonstration Files
Table below shows some examples of Voice Morphing Technology. The "Source Speech" column indicates the utterances of the source speaker, and the "Target Speech" column is the target speaker's utterances. The utterances in both these two columns are NOT included in the training data for the estimation of the conversion function. The next two columns, "Converted Speech 1" and "Converted Speech 2", are the results regenerated using the Voice Morphing technology. The difference between these two column is that the "Converted Speech 1" applies the target prosody extracted from the target utterance, but the "Converted Speech 2" still applies the original prosody of the source utterances. The reason to convert with different prosody is for the evaluation of prosody influence on speaker identification.
Source Speech
Target Speech
Converted Speech 1
Converted Speech 2
Female to Male
src01.wav
tgt01.wav
vc01.wav
vm01.wav
Male to Female
src02.wav
tgt02.wav
vc02.wav
vm02.wav
Female to Female
src03.wav
tgt03.wav
vc03.wav
vm03.wav
Male to Male
src04.wav
tgt04.wav
vc04.wav
vm04.wav
Bluetooth / SAN (Small Area Networks)
BLUE TOOTH
Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras, and video game consoles over a secure, globally unlicensed short-range radio frequency. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group.
Uses
A typical Bluetooth mobile phone headset
Bluetooth is a standard and communications protocol primarily designed for low power consumption, with a short range (power-class-dependent: 1 meter, 10 meters, 100 meters)[1] based on low-cost transceiver microchips in each device.
Bluetooth enables these devices to communicate with each other when they are in range. The devices use a radio communications system, so they do not have to be in line of sight of each other, and can even be in other rooms, as long as the received transmission is powerful enough.
| Class | Range | |
| Class 1 | 100 mW (20 dBm) | ~100 meters |
| Class 2 | 2.5 mW (4 dBm) | ~10 meters |
| Class 3 | 1 mW (0 dBm) | ~1 meter |
It has to be noted that in most cases the effective range of class 2 devices is extended if they connect to a class 1 transceiver, compared to pure class 2 network. This is accomplished by higher sensitivity and transmitter power of the Class 1 device. The higher transmitter power of Class 1 device allows higher power to be received by the Class 2 device. Furthermore, higher sensitivity of Class 1 device allows reception of much lower transmitted power of the Class 2 devices. Thus, allowing operation of Class 2 devices at much higher distances. Devices that use a power amplifier on the transmit, have improved receive sensitivity, and highly optimized antennas are available that routinely achieve ranges of 1km[2] within the Bluetooth Class 1 standard.
| Version | Data Rate |
| Version 1.2 | 1 Mbit/s |
| Version 2.0 + EDR | 3 Mbit/s |
| WiMedia Alliance | 53 - 480 Mbit/s |
Bluetooth profiles
Main article: Bluetooth profile
In order to use Bluetooth, a device must be compatible with certain Bluetooth profiles. These define the possible applications and uses of the technology.
List of applications
More prevalent applications of Bluetooth include:
- Wireless control of and communication between a mobile phone and a hands-free headset. This was one of the earliest applications to become popular.
- Wireless networking between PCs in a confined space and where little bandwidth is required.
- Wireless communications with PC input and output devices, the most common being the mouse, keyboard and printer.
- Transfer of files between devices with OBEX.
- Transfer of contact details, calendar appointments, and reminders between devices with OBEX.
- Replacement of traditional wired serial communications in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.
- For controls where infrared was traditionally used.
- Sending small advertisements from Bluetooth enabled advertising hoardings to other, discoverable, Bluetooth devices.
- Two seventh-generation game consoles—Nintendo's Wii[3] and Sony's PlayStation 3—use Bluetooth for their respective wireless controllers.
- Dial-up internet access on personal computer or PDA using a data-capable mobile phone as a modem.
- Receiving commercial advertisements ("spam") via a kiosk, e.g. at a movie theatre or lobby
Bluetooth vs. Wi-Fi in networking
Bluetooth and Wi-Fi have slightly different applications in today's offices, homes, and on the move: setting up networks, printing, or transferring presentations and files from PDAs to computers. Both are versions of unlicensed spread spectrum technology.
Bluetooth differs from Wi-Fi in that the latter provides higher throughput and covers greater distances, but requires more expensive hardware and higher power consumption. They use the same frequency range, but employ different multiplexing schemes. While Bluetooth is a cable replacement for a variety of applications, Wi-Fi is a cable replacement only for local area network access. Bluetooth is often thought of as wireless USB, whereas Wi-Fi is wireless Ethernet, both operating at much lower bandwidth than the cable systems they are trying to replace. However, this analogy is not entirely accurate since any Bluetooth device can, in theory, host any other Bluetooth device—something that is not universal to USB devices, therefore it would resemble more a wireless FireWire.
Bluetooth
![Bluetooth module from EZURiO with 300m range.[1] .](http://en.wikipedia.org/wiki/Image:Bism2pa.jpg)
Bluetooth module from EZURiO with 300m range.[1] .
Bluetooth exists in many products, such as phones, printers, modems and headsets. The technology is useful when transferring information between two or more devices that are near each other in low-bandwidth situations. Bluetooth is commonly used to transfer sound data with phones (i.e. with a Bluetooth headset) or byte data with hand-held computers (transferring files).
Bluetooth simplifies the discovery and setup of services between devices. Bluetooth devices advertise all of the services they provide. This makes using services easier because there is no longer a need to setup network addresses or permissions as in many other networks.
Wi-Fi
Wi-Fi is more like traditional Ethernet networks, and requires configuration to set up shared resources, transmit files, and to set up audio links (for example, headsets and hands-free devices). It uses the same radio frequencies as Bluetooth, but with higher power output resulting in a stronger connection. Wi-Fi is sometimes called "wireless Ethernet." This description is accurate as it also provides an indication of its relative strengths and weaknesses. Wi-Fi requires more setup, but is better suited for operating full-scale networks because it enables a faster connection, better range from the base station, and better security than Bluetooth.
Computer requirements
A typical Bluetooth USB dongle, shown here next to a metric ruler
An internal notebook Bluetooth card (14×36×4 mm)
A personal computer must have a Bluetooth adapter in order to be able to communicate with other Bluetooth devices (such as mobile phones, mice and keyboards). While some desktop computers already contain an internal Bluetooth adapter, most require an external Bluetooth dongle. Most recent laptops come with a built-in Bluetooth adapter.
Unlike its predecessor, IrDA, which requires a separate adapter for each device, Bluetooth allows multiple devices to communicate with a computer over a single adapter.
Operating system support
For more details on this topic, see Bluetooth stack.
Apple has supported Bluetooth since Mac OS X version 10.2 released in 2002. [4]
Of Microsoft platforms, Windows XP Service Pack 2 and later releases have native support for Bluetooth. Previous versions required the users to install their Bluetooth adapter's own drivers, which was not directly supported by Microsoft.[5] Microsoft's own Bluetooth dongles (that are packaged with their Bluetooth computer devices) have no external drivers and thus require at least Windows XP Service Pack 2.
Linux provides two Bluetooth stacks, with the BlueZ stack included with most Linux kernels. It was originally developed by Qualcomm and Affix. BlueZ supports all core Bluetooth protocols and layers.
NetBSD features bluetooth support since its 4.0 release[2]. Its bluetooth stack has been ported to FreeBSD and OpenBSD as well.
Specifications and features
The Bluetooth specification was developed in 1994 by Jaap Haartsen and Sven Mattisson, who were working for Ericsson Mobile Platforms in Lund, Sweden.[6] The specification is based on frequency-hopping spread spectrum technology.
The specifications were formalized by the Bluetooth Special Interest Group (SIG), organised by Mohd Syarifuddin. The SIG was formally announced on May 20, 1998. Today it has over 7000 companies worldwide. It was established by Ericsson, Sony Ericsson, IBM, Intel, Toshiba, and Nokia, and later joined by many other companies.
Bluetooth 1.0 and 1.0B
Versions 1.0 and 1.0B had many problems, and manufacturers had difficulties making their products interoperable. Versions 1.0 and 1.0B also had mandatory Bluetooth hardware device address (BD_ADDR) transmission in the Connecting process, rendering anonymity impossible at a protocol level, which was a major setback for certain services planned to be used in Bluetooth environments.
Bluetooth 1.1
- Ratified as IEEE Standard 802.15.1-2002.
- Many errors found in the 1.0B specifications were fixed.
- Added support for non-encrypted channels.
- Received Signal Strength Indicator (RSSI).
Bluetooth 1.2
This version is backward-compatible with 1.1 and the major enhancements include the following:
- Faster Connection and Discovery
- Adaptive frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence.
- Higher transmission speeds in practice, up to 721 kbit/s, as in 1.1.
- Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets.
- Host Controller Interface (HCI) support for three-wire UART.
- Ratified as IEEE Standard 802.15.1-2005.
Bluetooth 2.0
This version, specified on 10th November 2004[7], is backward-compatible with 1.1. The main enhancement is the introduction of an Enhanced Data Rate (EDR) of 3.0 Mbit/s. This has the following effects:[8]
- Three times faster transmission speed—up to 10 times in certain cases (up to 2.1 Mbit/s).
- Lower power consumption through a reduced duty cycle.
- Simplification of multi-link scenarios due to more available bandwidth.
The practical data transfer rate is 2.1 megabits per second and the basic signalling rate is about 3 megabits per second[9].
The "Bluetooth 2.0 + EDR" specification given at the Bluetooth Special Interest Group (SIG) includes EDR and there is no specification "Bluetooth 2.0" as used by many vendors. The HTC TyTN pocket PC phone, shows "Bluetooth 2.0 without EDR" on its data sheet[10] and another source states Bluetooth 2.0 without EDR is equivalent to version 1.2 with additional bug fixes[11]. In many cases it is not clear whether a product claiming to support "Bluetooth 2.0" actually supports the EDR higher transfer rate.
Bluetooth 2.1
Bluetooth Core Specification Version 2.1 is fully backward-compatible with 1.1, and was adopted by the Bluetooth SIG[12] on August 1, 2007.[13] This specification includes the following features:
- Extended inquiry response: provides more information during the inquiry procedure to allow better filtering of devices before connection. This information includes the name of the device, a list of services the device supports, as well as other information like the time of day, and pairing information.
- Sniff subrating: reduces the power consumption when devices are in the sniff low-power mode, especially on links with asymmetric data flows. Human interface devices (HID) are expected to benefit the most, with mouse and keyboard devices increasing the battery life by a factor of 3 to 10.
- Encryption Pause Resume: enables an encryption key to be refreshed, enabling much stronger encryption for connections that stay up for longer than 23.3 hours (one Bluetooth day).
- Secure Simple Pairing: radically improves the pairing experience for Bluetooth devices, while increasing the use and strength of security. It is expected that this feature will significantly increase the use of Bluetooth.[14]
- NFC cooperation: automatic creation of secure Bluetooth connections when NFC radio interface is also available. For example, a headset should be paired with a Bluetooth 2.1 phone including NFC just by bringing the two devices close to each other (a few centimeters). Another example is automatic uploading of photos from a mobile phone or camera to a digital picture frame just by bringing the phone or camera close to the frame [15] [16].
Future of Bluetooth
- Broadcast Channel: enables Bluetooth information points. This will drive the adoption of Bluetooth into cell phones, and enable advertising models based around users pulling information from the information points, and not based around the object push model that is used in a limited way today.
- Topology Management: enables the automatic configuration of the piconet topologies especially in scatternet situations that are becoming more common today. This should all be invisible to the users of the technology, while also making the technology just work.
- Alternate MAC PHY: enables the use of alternative MAC and PHY's for transporting Bluetooth profile data. The Bluetooth Radio will still be used for device discovery, initial connection and profile configuration, however when lots of data needs to be sent, the high speed alternate MAC PHY's will be used to transport the data. This means that the proven low power connection models of Bluetooth are used when the system is idle, and the low power per bit radios are used when lots of data needs to be sent.
- QoS improvements: enable audio and video data to be transmitted at a higher quality, especially when best effort traffic is being transmitted in the same piconet.
Bluetooth technology already plays a part in the rising Voice over IP (VOIP) scene, with Bluetooth headsets being used as wireless extensions to the PC audio system. As VOIP becomes more popular, and more suitable for general home or office users than wired phone lines, Bluetooth may be used in cordless handsets, with a base station connected to the Internet link.
High-speed Bluetooth
On 28 March 2006, the Bluetooth Special Interest Group announced its selection of the WiMedia Alliance Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) version of UWB for integration with current Bluetooth wireless technology.
UWB integration will create a version of Bluetooth wireless technology with a high-speed/high-data-rate option. This new version of Bluetooth technology will meet the high-speed demands of synchronizing and transferring large amounts of data, as well as enabling high-quality video and audio applications for portable devices, multi-media projectors and television sets, and wireless VOIP.
At the same time, Bluetooth technology will continue catering to the needs of very low power applications such as mice, keyboards, and mono headsets, enabling devices to select the most appropriate physical radio for the application requirements, thereby offering the best of both worlds.
Bluetooth 3.0
The next version of Bluetooth after v2.1, code-named
Ultra Low Power Bluetooth
On June 12, 2007, Nokia and Bluetooth SIG announced that Wibree will be a part of the Bluetooth specification as an ultra low power Bluetooth technology[17]. Expected use cases include watches displaying Caller ID information, sports sensors monitoring your heart rate during exercise, as well as medical devices. The Medical Devices Working Group is also creating a medical devices profile and associated protocols to enable this market.
Technical information
Communication and connection
A master Bluetooth device can communicate with up to seven devices. This network group of up to eight devices is called a piconet.
A piconet is an ad-hoc computer network, using Bluetooth technology protocols to allow one master device to interconnect with up to seven active devices. Up to 255 further devices can be inactive, or parked, which the master device can bring into active status at any time.
At any given time, data can be transferred between the master and one other device, however, the devices can switch roles and the slave can become the master at any time. The master switches rapidly from one device to another in a round-robin fashion. (Simultaneous transmission from the master to multiple other devices is possible, but not used much.)
Bluetooth specification allows connecting two or more piconets together to form a scatternet, with some devices acting as a bridge by simultaneously playing the master role and the slave role in one piconet. These devices are planned for 2007.
Many USB Bluetooth adapters are available, some of which also include an IrDA adapter. Older (pre-2003) Bluetooth adapters, however, have limited services, offering only the Bluetooth Enumerator and a less-powerful Bluetooth Radio incarnation. Such devices can link computers with Bluetooth, but they do not offer much in the way of services that modern adapters do.
Setting up connections
Any Bluetooth device will transmit the following sets of information on demand:
- Device name.
- Device class.
- List of services.
- Technical information, for example, device features, manufacturer, Bluetooth specification, clock offset.
Any device may perform an inquiry to find other devices to which to connect, and any device can be configured to respond to such inquiries. However, if the device trying to connect knows the address of the device, it always responds to direct connection requests and transmits the information shown in the list above if requested. Use of device services may require pairing or acceptance by its owner, but the connection itself can be started by any device and held until it goes out of range. Some devices can be connected to only one device at a time, and connecting to them prevents them from connecting to other devices and appearing in inquiries until they disconnect from the other device.
Every device has a unique 48-bit address. However these addresses are generally not shown in inquiries. Instead, friendly Bluetooth names are used, which can be set by the user. This name appears when another user scans for devices and in lists of paired devices.
Most phones have the Bluetooth name set to the manufacturer and model of the phone by default. Most phones and laptops show only the Bluetooth names and special programs that are required to get additional information about remote devices. This can be confusing as, for example, there could be several phones in range named T610 (see Bluejacking).
Pairing
Pairs of devices may establish a trusted relationship by learning (by user input) a shared secret known as a passkey. A device that wants to communicate only with a trusted device can cryptographically authenticate the identity of the other device. Trusted devices may also encrypt the data that they exchange over the air so that no one can listen in. The encryption can, however, be turned off, and passkeys are stored on the device file system, not on the Bluetooth chip itself. Since the Bluetooth address is permanent, a pairing is preserved, even if the Bluetooth name is changed. Pairs can be deleted at any time by either device. Devices generally require pairing or prompt the owner before they allow a remote device to use any or most of their services. Some devices, such as Sony Ericsson phones, usually accept OBEX business cards and notes without any pairing or prompts.
Certain printers and access points allow any device to use its services by default, much like unsecured Wi-Fi networks. Pairing algorithms are sometimes manufacturer-specific for transmitters and receivers used in applications such as music and entertainment.
Air interface
The protocol operates in the license-free ISM band at 2.4-2.4835 GHz. To avoid interfering with other protocols that use the 2.45 GHz band, the Bluetooth protocol divides the band into 79 channels (each 1 MHz wide) and changes channels up to 1600 times per second. Implementations with versions 1.1 and 1.2 reach speeds of 723.1 kbit/s. Version 2.0 implementations feature Bluetooth Enhanced Data Rate (EDR) and reach 2.1 Mbit/s. Technically, version 2.0 devices have a higher power consumption, but the three times faster rate reduces the transmission times, effectively reducing power consumption to half that of 1.x devices (assuming equal traffic load).
Security
Bluetooth implements confidentiality, authentication and key derivation with custom algorithms based on the SAFER+ block cipher. In Bluetooth, key generation is generally based on a Bluetooth PIN, which has to be entered into both devices. This procedure might get modified slightly, if one of the devices has a fixed PIN, which is the case e.g. for headsets or similar devices with a restricted user interface. Foremost, an initialization key or master key is generated, using the E22 algorithm [18].
The E0 stream cipher is used for encrypting packets, granting confidentiality and is based on a shared cryptographic secret, namely a previously generated link key or master key. Those keys, used for subsequent encryption of data sent via the air interface, hardly rely on the Bluetooth PIN, which has been entered into one or both devices.
A demonstration of this reduction has been put effort in by Y. Shaked and A. Wool in [19]. An overview of the most important vulnerabilities and the most common exploits to those vulnerabilities is presented in [20].
Social concerns
Security concerns
2003:
In November 2003, Ben and Adam Laurie from A.L. Digital Ltd. discovered that serious flaws in Bluetooth security may lead to disclosure of personal data.[21] It should be noted, however, that the reported security problems concerned some poor implementations of Bluetooth, rather than the protocol itself.
In a subsequent experiment, Martin Herfurt from the trifinite.group was able to do a field-trial at the CeBIT fairgrounds, showing the importance of the problem to the world. A new attack called BlueBug was used for this experiment.[22]
This is one of a number of concerns that have been raised over the security of Bluetooth communications. In 2004 the first purported virus using Bluetooth to spread itself among mobile phones appeared on the Symbian OS.[23] The virus was first described by Kaspersky Lab and requires users to confirm the installation of unknown software before it can propagate.
The virus was written as a proof-of-concept by a group of virus writers known as 29A and sent to anti-virus groups. Thus, it should be regarded as a potential (but not real) security threat to Bluetooth or Symbian OS since the virus has never spread in the wild.
In August 2004, a world-record-setting experiment (see also Bluetooth sniping) showed that the range of Class 2 Bluetooth radios could be extended to 1.78 km (1.08 mile) with directional antennas and signal amplifiers.[24] This poses a potential security threat because it enables attackers to access vulnerable Bluetooth-devices from a distance beyond expectation. The attacker must also be able to receive information from the victim to set up a connection. No attack can be made against a Bluetooth device unless the attacker knows its Bluetooth address and which channels to transmit on.
2005:
In April 2005, Cambridge University security researchers published results of their actual implementation of passive attacks against the PIN-based pairing between commercial Bluetooth devices, confirming the attacks to be practicably fast and the Bluetooth symmetric key establishment method to be vulnerable. To rectify this vulnerability, they carried out an implementation which showed that stronger, asymmetric key establishment is feasible for certain classes of devices, such as handphones.[25]
In June 2005, Yaniv Shaked and Avishai Wool published the paper "Cracking the Bluetooth PIN1," which shows both passive and active methods for obtaining the PIN for a Bluetooth link. The passive attack allows a suitably equipped attacker to eavesdrop on communications and spoof if they were present at the time of initial pairing. The active method makes use of a specially constructed message that must be inserted at a specific point in the protocol, to make the master and slave repeat the pairing process. After that, the first method can be used to crack the PIN. This attack's major weakness is that it requires the user of the devices under attack to re-enter the PIN during the attack when the device prompts them to. Also, this active attack probably requires custom hardware, since most commercially available Bluetooth devices are not capable of the timing necessary.[26]
In August 2005, police in Cambridgeshire,
2006:
In April 2006, researchers from Secure Network and F-Secure published a report that warns of the large number of devices left in a visible state, and issued statistics on the spread of various Bluetooth services and the ease of spread of an eventual Bluetooth worm.[28]
In October 2006, at the Luxemburgish Hack.lu Security Conference, Kevin Finistere and Thierry Zoller demonstrated and released a remote root shell over Bluetooth on Mac OSX 10.3.9 and 10.4. They also demonstrated the first Bluetooth PIN and Linkkeys cracker, which is based on the research of Wool and Shaked.
Bluejacking:
Bluejacking allows phone users to send business cards anonymously using Bluetooth wireless technology. Bluejacking does NOT involve the removal or alteration of any data from the device. These business cards often have a clever or flirtatious message rather than the typical name and phone number. Bluejackers often look for the receiving phone to ping or the user to react. They then send another, more personal message to that device. Once again, in order to carry out a bluejacking, the sending and receiving devices must be within range of each other, which is typically 10 meters for most mobile devices. Phone owners who receive bluejack messages should refuse to add the contacts to their address book. Devices that are set in non-discoverable mode are not susceptible to bluejacking. However, the use of the Linux application Redfang, allows this to be bypassed. [3]
Health concerns
Bluetooth uses the microwave radio frequency spectrum in the 2.4 GHz to 2.4835 GHz range. Maximum power output from a Bluetooth radio is 1 mW, 2.5 mW, and 100 mW for Class 3, Class 2, and Class 1 devices respectively, which puts Class 1 at roughly the same level as cell phones, and the other two classes much lower.[29] Accordingly, Class 2 and Class 3 Bluetooth devices are considered less of a potential hazard than cell phones, and Class 1 may be comparable to that of cell phones.
Origin of the name and the logo
Bluetooth was named after a late tenth century king, Harald Bluetooth, King of Denmark and Norway. He is known for his unification of previously warring tribes from
The name may have been inspired less by the historical Harald than the loose interpretation of him in The Long Ships by Frans Gunnar Bengtsson, a Swedish Viking-inspired novel.
The Bluetooth logo merges the Germanic runes analogous to the modern Latin letter H and B: 
(Hagall) and (Berkanan) merged together, forming a bind rune.
Bluetooth Special Interest Group
In 1998, Ericsson, IBM, Intel, Toshiba, and Nokia, formed a consortium and adopted the code name Bluetooth for their proposed open specification. In December 1999, 3Com, Lucent Technologies, Microsoft, and Motorola joined the initial founders as the promoter of Bluetooth Special Interest Group (SIG). Since that time, Lucent Technologies transferred their membership to their spinoff Agere Systems, and 3Com has left the promoter group. Agere Systems was later merged with LSI Corporation and left the Bluetooth promoters group in August 2007.
The Bluetooth Special Interest Group (SIG) is a privately held, not-for-profit trade association with headquarters in
USB / Universal Serial Bus
Microprocessor
A microprocessor incorporates the functions of a central processing unit (CPU) on a single integrated circuit (IC). [1] The first microprocessors used a word size of only 4 bits, so that the transistors of its logic circuits would fit onto a single part. One or more microprocessors typically serve as the processing elements of a computer system, embedded system, or handheld device. Microprocessors made possible the advent of the microcomputer in the mid-1970s. Before this period, CPUs were typically made from small-scale integrated circuits containing the equivalent of only a few transistors. By integrating the processor onto one or a very few large-scale integrated circuit packages (containing the equivalent of thousands or millions of discrete transistors), the cost of processing capacity was greatly reduced. Since the advent of the microprocessor in the mid 1970's, it has now become the most prevalent implementation of the CPU, almost completely replacing all other forms. See History of computing hardware for pre-electronic and early electronic computers.
Since the early 1970s, the increase in processing capacity of evolving microprocessors has been known to generally follow Moore's Law. It suggests that the complexity of an integrated circuit, with respect to minimum component cost, doubles every 18 months. In the early 1990s, microprocessor's heat generation (TDP) - due to current leakage - emerged as a leading developmental constraint[2]. From their humble beginnings as the drivers for calculators, the continued increase in processing capacity has led to the dominance of microprocessors over every other form of computer; every system from the largest mainframes to the smallest handheld computers now uses a microprocessor at its core.
Contents
[hide]
1 History
1.1 First types
1.2 Notable 8-bit designs
1.3 16-bit designs
1.4 32-bit designs
1.5 64-bit designs in personal computers
1.6 Multicore designs
1.7 RISC
2 Special-purpose designs
3 Market statistics
4 Architectures
5 See also
5.1 Major designers
6 References
7 External links
7.1 General
7.2 Historical documents
History
First types
The 4004 with cover removed (left) and as actually used (right).
Three projects arguably delivered a complete microprocessor at about the same time, namely Intel's 4004, the Texas Instruments (TI) TMS 1000, and Garrett AiResearch's Central Air Data Computer (CADC).
In 1968, Garrett AiResearch, with designer Ray Holt and Steve Geller, were invited to produce a digital computer to compete with electromechanical systems then under development for the main flight control computer in the US Navy's new F-14 Tomcat fighter. The design was complete by 1970, and used a MOS-based chipset as the core CPU. The design was significantly (approximately 20 times) smaller and much more reliable than the mechanical systems it competed against, and was used in all of the early Tomcat models. This system contained a "a 20-bit, pipelined, parallel multi-microprocessor". However, the system was considered so advanced that the Navy refused to allow publication of the design until 1997. For this reason the CADC, and the MP944 chipset it used, are fairly unknown even today. (see First Microprocessor Chip Set.) TI developed the 4-bit TMS 1000, and stressed pre-programmed embedded applications, introducing a version called the TMS1802NC on September 17, 1971, which implemented a calculator on a chip. The Intel chip was the 4-bit 4004, released on November 15, 1971, developed by Federico Faggin and Marcian Hoff.
TI filed for the patent on the microprocessor. Gary Boone was awarded U.S. Patent 3,757,306 for the single-chip microprocessor architecture on September 4, 1973. It may never be known which company actually had the first working microprocessor running on the lab bench. In both 1971 and 1976, Intel and TI entered into broad patent cross-licensing agreements, with Intel paying royalties to TI for the microprocessor patent. A nice history of these events is contained in court documentation from a legal dispute between Cyrix and Intel, with TI as intervenor and owner of the microprocessor patent.
Interestingly, a third party (Gilbert Hyatt) was awarded a patent which might cover the "microprocessor". See a webpage claiming an invention pre-dating both TI and Intel, describing a "microcontroller". According to a rebuttal and a commentary, the patent was later invalidated, but not before substantial royalties were paid out.
A computer-on-a-chip is a variation of a microprocessor which combines the microprocessor core (CPU), some memory, and I/O (input/output) lines, all on one chip. The computer-on-a-chip patent, called the "microcomputer patent" at the time, U.S. Patent 4,074,351 , was awarded to Gary Boone and Michael J. Cochran of TI. Aside from this patent, the standard meaning of microcomputer is a computer using one or more microprocessors as its CPU(s), while the concept defined in the patent is perhaps more akin to a microcontroller.
According to A History of Modern Computing, (MIT Press), pp. 220–21, Intel entered into a contract with Computer Terminals Corporation, later called Datapoint, of San Antonio TX, for a chip for a terminal they were designing. Datapoint later decided to use the chip, and Intel marketed it as the 8008 in April, 1972. This was the world's first 8-bit microprocessor. It was the basis for the famous "Mark-8" computer kit advertised in the magazine Radio-Electronics in 1974. The 8008 and its successor, the world-famous 8080, opened up the microprocessor component marketplace.
Notable 8-bit designs
The 4004 was later followed in 1972 by the 8008, the world's first 8-bit microprocessor. These processors are the precursors to the very successful Intel 8080 (1974), Zilog Z80 (1976), and derivative Intel 8-bit processors. The competing Motorola 6800 was released August 1974. Its architecture was cloned and improved in the MOS Technology 6502 in 1975, rivaling the Z80 in popularity during the 1980s.
Both the Z80 and 6502 concentrated on low overall cost, through a combination of small packaging, simple computer bus requirements, and the inclusion of circuitry that would normally have to be provided in a separate chip (for instance, the Z80 included a memory controller). It was these features that allowed the home computer "revolution" to take off in the early 1980s, eventually delivering such inexpensive machines as the Sinclair ZX-81, which sold for US$99.
The Western Design Center, Inc. (WDC) introduced the CMOS 65C02 in 1982 and licensed the design to several companies which became the core of the Apple IIc and IIe personal computers, medical implantable grade pacemakers and defibrilators, automotive, industrial and consumer devices.WDC pioneered the licensing of microprocessor technology which was later followed by ARM and other microprocessor Intellectual Property (IP) providers in the 1990’s.
Motorola trumped the entire 8-bit world by introducing the MC6809 in 1978, arguably one of the most powerful, orthogonal, and clean 8-bit microprocessor designs ever fielded – and also one of the most complex hard-wired logic designs that ever made it into production for any microprocessor. Microcoding replaced hardwired logic at about this point in time for all designs more powerful than the MC6809 – specifically because the design requirements were getting too complex for hardwired logic.
Another early 8-bit microprocessor was the Signetics 2650, which enjoyed a brief flurry of interest due to its innovative and powerful instruction set architecture.
A seminal microprocessor in the world of spaceflight was RCA's RCA 1802 (aka CDP1802, RCA COSMAC) (introduced in 1976) which was used in NASA's Voyager and Viking spaceprobes of the 1970s, and onboard the Galileo probe to Jupiter (launched 1989, arrived 1995). RCA COSMAC was the first to implement C-MOS technology. The CDP1802 was used because it could be run at very low power,* and because its production process (Silicon on Sapphire) ensured much better protection against cosmic radiation and electrostatic discharges than that of any other processor of the era. Thus, the 1802 is said to be the first radiation-hardened microprocessor.
16-bit designs
The first multi-chip 16-bit microprocessor was the National Semiconductor IMP-16, introduced in early 1973. An 8-bit version of the chipset was introduced in 1974 as the IMP-8. During the same year, National introduced the first 16-bit single-chip microprocessor, the National Semiconductor PACE, which was later followed by an NMOS version, the INS8900.
Other early multi-chip 16-bit microprocessors include one used by Digital Equipment Corporation (DEC) in the LSI-11 OEM board set and the packaged PDP 11/03 minicomputer, and the Fairchild Semiconductor MicroFlame 9440, both of which were introduced in the 1975 to 1976 timeframe.
The first single-chip 16-bit microprocessor was TI's TMS 9900, which was also compatible with their TI-990 line of minicomputers. The 9900 was used in the TI 990/4 minicomputer, the TI-99/4A home computer, and the TM990 line of OEM microcomputer boards. The chip was packaged in a large ceramic 64-pin DIP package, while most 8-bit microprocessors such as the Intel 8080 used the more common, smaller, and less expensive plastic 40-pin DIP. A follow-on chip, the TMS 9980, was designed to compete with the Intel 8080, had the full TI 990 16-bit instruction set, used a plastic 40-pin package, moved data 8 bits at a time, but could only address 16 KB. A third chip, the TMS 9995, was a new design. The family later expanded to include the 99105 and 99110.
The Western Design Center, Inc. (WDC) introduced the CMOS 65816 16-bit upgrade of the WDC CMOS 65C02 in 1984. The 65816 16-bit microprocessor was the core of the Apple IIgs and later the Super Nintendo Entertainment System, making it one of the most popular 16-bit designs of all time.
Intel followed a different path, having no minicomputers to emulate, and instead "upsized" their 8080 design into the 16-bit Intel 8086, the first member of the x86 family which powers most modern PC type computers. Intel introduced the 8086 as a cost effective way of porting software from the 8080 lines, and succeeded in winning much business on that premise. The 8088, a version of the 8086 that used an external 8-bit data bus, was the microprocessor in the first IBM PC, the model 5150. Following up their 8086 and 8088, Intel released the 80186, 80286 and, in 1985, the 32-bit 80386, cementing their PC market dominance with the processor family's backwards compatibility.
The integrated microprocessor memory management unit (MMU) was developed by Childs et al. of Intel, and awarded US patent number 4,442,484.
32-bit designs
Upper interconnect layers on an Intel 80486DX2 die.
16-bit designs were in the market only briefly when full 32-bit implementations started to appear.
The most significant of the 32-bit designs is the MC68000, introduced in 1979. The 68K, as it was widely known, had 32-bit registers but used 16-bit internal data paths, and a 16-bit external data bus to reduce pin count, and supported only 24-bit addresses. Motorola generally described it as a 16-bit processor, though it clearly has 32-bit architecture. The combination of high speed, large (16 megabytes (2^24)) memory space and fairly low costs made it the most popular CPU design of its class. The Apple Lisa and Macintosh designs made use of the 68000, as did a host of other designs in the mid-1980s, including the Atari ST and Commodore Amiga.
The world's first single-chip fully-32-bit microprocessor, with 32-bit data paths, 32-bit buses, and 32-bit addresses, was the AT&T Bell Labs BELLMAC-32A, with first samples in 1980, and general production in 1982 (See this bibliographic reference and this general reference). After the divestiture of AT&T in 1984, it was renamed the WE 32000 (WE for Western Electric), and had two follow-on generations, the WE 32100 and WE 32200. These microprocessors were used in the AT&T 3B5 and 3B15 minicomputers; in the 3B2, the world's first desktop supermicrocomputer; in the "Companion", the world's first 32-bit laptop computer; and in "Alexander", the world's first book-sized supermicrocomputer, featuring ROM-pack memory cartridges similar to today's gaming consoles. All these systems ran the UNIX System V operating system.
Intel's first 32-bit microprocessor was the iAPX 432, which was introduced in 1981 but was not a commercial success. It had an advanced capability-based object-oriented architecture, but poor performance compared to other competing architectures such as the Motorola 68000.
Motorola's success with the 68000 led to the MC68010, which added virtual memory support. The MC68020, introduced in 1985 added full 32-bit data and address busses. The 68020 became hugely popular in the Unix supermicrocomputer market, and many small companies (e.g., Altos, Charles River Data Systems) produced desktop-size systems. Following this with the MC68030, which added the MMU into the chip, the 68K family became the processor for everything that wasn't running DOS. The continued success led to the MC68040, which included an FPU for better math performance. A 68050 failed to achieve its performance goals and was not released, and the follow-up MC68060 was released into a market saturated by much faster RISC designs. The 68K family faded from the desktop in the early 1990s.
Other large companies designed the 68020 and follow-ons into embedded equipment. At one point, there were more 68020s in embedded equipment than there were Intel Pentiums in PCs (See this webpage for this embedded usage information). The ColdFire processor cores are derivatives of the venerable 68020.
During this time (early to mid 1980s), National Semiconductor introduced a very similar 16-bit pinout, 32-bit internal microprocessor called the NS 16032 (later renamed 32016), the full 32-bit version named the NS 32032, and a line of 32-bit industrial OEM microcomputers. By the mid-1980s, Sequent introduced the first symmetric multiprocessor (SMP) server-class computer using the NS 32032. This was one of the design's few wins, and it disappeared in the late 1980s.
The MIPS R2000 (1984) and R3000 (1989) were highly successful 32-bit RISC microprocessors. They were used in high-end workstations and servers by SGI, among others.
Other designs included the interesting Zilog Z8000, which arrived too late to market to stand a chance and disappeared quickly.
In the late 1980s, "microprocessor wars" started killing off some of the microprocessors. Apparently, with only one major design win, Sequent, the NS 32032 just faded out of existence, and Sequent switched to Intel microprocessors.
From 1985 to 2003, the 32-bit x86 architectures became increasingly dominant in desktop, laptop, and server markets, and these microprocessors became faster and more capable. Intel had licensed early versions of the architecture to other companies, but declined to license the Pentium, so AMD and Cyrix built later versions of the architecture based on their own designs. During this span, these processors increased in complexity (transistor count) and capability (instructions/second) by at least a factor of 1000. Intel's Pentium line is probably the most famous and recognizable 32-bit processor model, at least with the public at large.
64-bit designs in personal computers
While 64-bit microprocessor designs have been in use in several markets since the early 1990s, the early 2000s saw the introduction of 64-bit microchips targeted at the PC market.
With AMD's introduction of the first 64-bit IA-32 backwards-compatible architecture, AMD64, in September 2003, followed by Intel's own x86-64 chips, the 64-bit desktop era began. Both processors can run 32-bit legacy apps as well as the new 64-bit software. With 64-bit Windows XP, Windows Vista x64, Linux and Mac OS X (to a certain extent) that run 64-bit native, the software too is geared to utilize the full power of such processors. The move to 64 bits is more than just an increase in register size from the IA-32 as it also doubles the number of general-purpose registers for the aging CISC designs.
The move to 64 bits by PowerPC processors had been intended since the processors' design in the early 90s and was not a major cause of incompatibility. Existing integer registers are extended as are all related data pathways, but, as was the case with IA-32, both floating point and vector units had been operating at or above 64 bits for several years. Unlike what happened with IA-32 was extended to x86-64, no new general purpose registers were added in 64-bit PowerPC, so any performance gained when using the 64-bit mode for applications making no use of the larger address space is minimal.
Multicore designs
AMD Athlon 64 X2 3600 Dual core processor
Main article: Multi-core (computing)
A different approach to improving a computer's performance is to add extra processors, as in symmetric multiprocessing designs which have been popular in servers and workstations since the early 1990s. Keeping up with Moore's Law is becoming increasingly challenging as chip-making technologies approach the physical limits of the technology.
In response, the microprocessor manufacturers look for other ways to improve performance, in order to hold on to the momentum of constant upgrades in the market.
A multi-core processor is simply a single chip containing more than one microprocessor core, effectively multiplying the potential performance with the number of cores (as long as the operating system and software is designed to take advantage of more than one processor). Some components, such as bus interface and second level cache, may be shared between cores. Because the cores are physically very close they interface at much faster clock speeds compared to discrete multiprocessor systems, improving overall system performance.
In 2005, the first mass-market dual-core processors were announced and as of 2007 dual-core processors are widely used in servers, workstations and PCs while quad-core processors are now available for high-end applications in both the home and professional environments.
Sun Microsystems has released the Niagara and Niagara 2 chips, both of which feature an eight-core design. The Niagara 2 supports more threads and operates at 1.6 GHz.
RISC
In the mid-1980s to early-1990s, a crop of new high-performance RISC (reduced instruction set computer) microprocessors appeared, which were initially used in special purpose machines and Unix workstations, but then gained wide acceptance in other roles.
The first commercial design was released by MIPS Technologies, the 32-bit R2000 (the R1000 was not released). The R3000 made the design truly practical, and the R4000 introduced the world's first 64-bit design. Competing projects would result in the IBM POWER and Sun SPARC systems, respectively. Soon every major vendor was releasing a RISC design, including the AT&T CRISP, AMD 29000, Intel i860 and Intel i960, Motorola 88000, DEC Alpha and the HP-PA.
Market forces have "weeded out" many of these designs, with almost no desktop or laptop RISC processors and with the SPARC being used in Sun designs only. MIPS is primarily used in embedded systems, notably in Cisco routers. The rest of the original crop of designs have disappeared. Other companies have attacked niches in the market, notably ARM, originally intended for home computer use but since focussed at the embedded processor market. Today RISC designs based on the MIPS, ARM or PowerPC core power the vast majority of computing devices.
As of 2007, two 64-bit RISC architectures are still produced in volume: SPARC and Power Architecture. The RISC-like Itanium is produced in smaller quantities. The vast majority of 64-bit microprocessors are now x86-64 CISC designs from AMD and Intel.
Special-purpose designs
A 4-bit, 2 register, six assembly language instruction computer made entirely of 74-series chips.
Though the term "microprocessor" has traditionally referred to a single- or multi-chip CPU or system-on-a-chip (SoC), several types of specialized processing devices have followed from the technology. The most common examples are microcontrollers, digital signal processors (DSP) and graphics processing units (GPU). Many examples of these are either not programmable, or have limited programming facilities. For example, in general GPUs through the 1990s were mostly non-programmable and have only recently gained limited facilities like programmable vertex shaders. There is no universal consensus on what defines a "microprocessor", but it is usually safe to assume that the term refers to a general-purpose CPU of some sort and not a special-purpose processor unless specifically noted.
The RCA 1802 had what is called a static design, meaning that the clock frequency could be made arbitrarily low, even to 0 Hz, a total stop condition. This let the Voyager/Viking/Galileo spacecraft use minimum electric power for long uneventful stretches of a voyage. Timers and/or sensors would awaken/speed up the processor in time for important tasks, such as navigation updates, attitude control, data acquisition, and radio communication.
Market statistics
In 2003, about $44 billion (USD) worth of microprocessors were manufactured and sold. [1] Although about half of that money was spent on CPUs used in desktop or laptop personal computers, those count for only about 0.2% of all CPUs sold.
Silicon Valley has an old saying: "The first chip costs a million dollars; the second one costs a nickel." In other words, most of the cost is in the design and the manufacturing setup: once manufacturing is underway, it costs almost nothing.[citation needed]
About 55% of all CPUs sold in the world are 8-bit microcontrollers. Over 2 billion 8-bit microcontrollers were sold in 1997. [2]
Less than 10% of all the CPUs sold in the world are 32-bit or more. Of all the 32-bit CPUs sold, about 2% are used in desktop or laptop personal computers, the rest are sold in household appliances such as toasters, microwaves, vacuum cleaners and televisions. "Taken as a whole, the average price for a microprocessor, microcontroller, or DSP is just over $6." [3]
Architectures
65xx
MOS Technology 6502
Western Design Center 65xx
ARM family
Altera Nios, Nios II
Atmel AVR architecture (purely microcontrollers)
EISC
RCA 1802 (aka RCA COSMAC, CDP1802)
DEC Alpha
Intel
Intel 4004, 4040
Intel 8080, 8085, Zilog Z80
Intel Itanium
Intel i860
Intel i960
LatticeMico32
M32R architecture
MIPS architecture
Motorola
Motorola 6800
Motorola 6809
Motorola 68000 family, ColdFire
Motorola 88000 (parent of PowerPC family, with POWER)
IBM POWER, parent of PowerPC family, with 88000
PowerPC family, G3, G4, G5
NSC 320xx
OpenCores OpenRISC architecture
PA-RISC family
National Semiconductor SC/MP ("scamp")
Signetics 2650
SPARC
SuperH family
Transmeta Crusoe, Efficeon (VLIW architectures, IA-32 32-bit Intel x86 emulator)
INMOS Transputer
x86 architecture
Intel 8086, 8088, 80186, 80188 (16-bit real mode-only x86 architecture)
Intel 80286 (16-bit real mode and protected mode x86 architecture)
IA-32 32-bit x86 architecture
x86-64 64-bit x86 architecture
XAP processor from Cambridge Consultants
Xilinx
MicroBlaze soft processor
PowerPC405 embedded hard processor in Virtex FPGAs
Universal Serial Bus
.
USBUniversal Serial Bus
Original USB Logo
Year created:
January 1996
Width:
1 bit
Number of devices:
127 per host controller
Capacity
12 or 480 Mbit/s
Style:
Serial
Hotplugging?
Yes
External?
Yes
A USB Series “A” plug, the most common USB plug
The USB "trident" Icon
Universal Serial Bus (USB) is a serial bus standard to interface devices. USB was designed to allow peripherals to be connected using a single standardized interface socket and to improve plug-and-play capabilities by allowing devices to be connected and disconnected without rebooting the computer (hot swapping). Other convenient features include providing power to low-consumption devices without the need for an external power supply and allowing many devices to be used without requiring manufacturer specific, individual device drivers to be installed.
USB is intended to help retire all legacy varieties of serial and parallel ports. USB can connect computer peripherals such as mouse devices, keyboards, PDAs, gamepads and joysticks, scanners, digital cameras, printers, personal media players, and flash drives. For many of those devices USB has become the standard connection method. USB is also used extensively to connect non-networked printers; USB simplifies connecting several printers to one computer. The large volume of USB memory devices and their ease of use has created a security concern that is often overlooked. USB lock software can lock out memory devices and still allow other USB peripherals to function. The USB was originally designed for personal computers, but it has become commonplace on other devices such as PDAs and video game consoles. In 2004, there were about 1 billion USB devices in the world.[1]
The design of USB is standardized by the USB Implementers Forum (USB-IF), an industry standards body incorporating leading companies from the computer and electronics industries. Notable members have included Agere, Apple Inc., Hewlett-Packard, Intel, NEC, and Microsoft.
History
The USB 1.0 specification was introduced in November 1995. USB was promoted by Intel (UHCI and open software stack), Microsoft (Windows software stack), Philips (Hub, USB-Audio), and US Robotics. USB was also the primary connector on the original iMac introduced 6 May 1998, including the connector for its new keyboard and mouse[2]. Originally USB was intended to replace the multitude of connectors at the back of PCs, as well as to simplify software configuration of communication devices. USB 1.1 came out in September 1998 to help rectify the adoption problems that occurred with earlier iterations of USB.[3]
As of 2008, the USB specification is at version 2.0 (with revisions). Hewlett-Packard, Intel, Lucent (now Alcatel-Lucent), Microsoft, NEC, and Philips jointly led the initiative to develop a higher data transfer rate than the 1.1 specification. The USB 2.0 specification was released in April 2000 and was standardized by the USB-IF at the end of 2001. Equipment conforming with any version of the standard will also work with devices designed to any previous specification (known as backward compatibility). Smaller USB plugs and receptacles for use in handheld and mobile devices, called Mini-B, were added to USB specification in the first engineering change notice. A new variant of smaller USB plugs and receptacles, Micro-USB, was announced by the USB Implementers Forum on January 4, 2007.[4]
Overview
A conventional USB hub
A USB system has an asymmetric design, consisting of a host, a multitude of downstream USB ports, and multiple peripheral devices connected in a tiered-star topology. Additional USB hubs may be included in the tiers, allowing branching into a tree structure, subject to a limit of 5 levels of tiers. USB host may have multiple host controllers and each host controller may provide one or more USB ports. Up to 127 devices, including the hub devices, may be connected to a single host controller.
USB devices are linked in series through hubs. There always exists one hub known as the root hub, which is built-in to the host controller. So-called "sharing hubs" also exist; allowing multiple computers to access the same peripheral device(s), either switching access between PCs automatically or manually. They are popular in small-office environments. In network terms they converge rather than diverge branches.
A single physical USB device may consist of several logical sub-devices that are referred to as device functions, because each individual device may provide several functions, such as a webcam (video device function) with a built-in microphone (audio device function).
USB endpoints actually reside on the connected device: the channels to the host are referred to as pipes
USB device communication is based on pipes (logical channels). Pipes are connections from the host controller to a logical entity on the device named an endpoint. The term endpoint is also occasionally used to refer to the pipe. A USB device can have up to 32 active pipes, 16 into the host controller and 16 out of the controller. Each endpoint can transfer data in one direction only, either into or out of the device, so each pipe is uni-directional. Endpoints are grouped into interfaces and each interface is associated with a single device function. An exception to this is endpoint zero, which is used for device configuration and which is not associated with any interface.
When a new USB device is connected to a USB host, the USB device enumeration process is started. The enumeration process first sends a reset signal to the USB device. The speed of the USB device is determined during the reset signaling. After reset, USB device setup information is read from the device by the host and the device is assigned a unique host-controller specific 7-bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to configured state. If the USB host is restarted, the enumeration process is repeated for all connected devices.
The host controller polls the bus for traffic, usually in a round-robin fashion, so no USB device can transfer any data on the bus without an explicit request from the host controller.
Host controllers
The computer hardware that contains the host controller and the root hub has an interface geared toward the programmer which is called Host Controller Device (HCD) and is defined by the hardware implementer.
In the version 1.x age, there were two competing HCD implementations, Open Host Controller Interface (OHCI) and Universal Host Controller Interface (UHCI). OHCI was developed by Compaq, Microsoft and National Semiconductor; UHCI was by Intel.
A typical USB connector.
VIA Technologies licensed the UHCI standard from Intel; all other chipset implementers use OHCI. UHCI is more software-driven, making UHCI slightly more processor-intensive than OHCI but cheaper to implement. The dueling implementations forced operating system vendors and hardware vendors to develop and test on both implementations which increased cost.
During the design phase of USB 2.0 the USB-IF insisted on only one implementation. The USB 2.0 HCD implementation is called the Enhanced Host Controller Interface (EHCI). Only EHCI can support hi-speed transfers. Most of PCI-based EHCI controllers contain other HCD implementations called 'companion host controller' to support Full Speed and Low Speed devices. The virtual HCD on Intel and VIA EHCI controllers are UHCI. All other vendors use virtual OHCI controllers.
HCD standards are out of the USB specification's scope, and the USB specification does not specify any HCD interfaces.
Device classes
Devices that attach to the bus can be full-custom devices requiring a full-custom device driver to be used, or may belong to a device class. These classes define an expected behavior in terms of device and interface descriptors so that the same device driver may be used for any device that claims to be a member of a certain class. An operating system is supposed to implement all device classes so as to provide generic drivers for any USB device. Device classes are decided upon by the Device Working Group of the USB Implementers Forum.
Device classes include:[5]
Class
Usage
Description
Examples
00h
Device
Unspecifiedclass 0
(Device class is unspecified. Interface descriptors are used for determining the required drivers.)
01h
Interface
Audio
speaker, microphone, sound card
02h
Both
Communications and CDC Control
ethernet adapter, modem, serial port adapter
03h
Interface
Human Interface Device (HID)
keyboard, mouse
05h
Interface
Physical Interface Device (PID)
force feedback joystick
06h
Interface
Image
digital camera
07h
Interface
Printer
laser printer Inkjet printer
08h
Interface
Mass Storage
USB flash drive, memory card reader, digital audio player
09h
Device
USB hub
full speed hub, hi-speed hub
0Ah
Interface
CDC-Data
(This class is used together with class 02h - Communications and CDC Control.)
0Bh
Interface
Smart Card
USB smart card reader
0Dh
Interface
Content Security
-
0Eh
Interface
Video
webcam
0Fh
Interface
Personal Healthcare
-
DCh
Both
Diagnostic Device
USB compliance testing device
E0h
Interface
Wireless Controller
Wi-Fi adapter, Bluetooth adapter
EFh
Both
Miscellaneous
ActiveSync device
FEh
Interface
Application Specific
IrDA Bridge
FFh
Both
Vendor Specific
(This class code indicates that the device needs vendor specific drivers.)
Note class 0: Use class information in the Interface Descriptors. This base class is defined to be used in Device Descriptors to indicate that class information should be determined from the Interface Descriptors in the device.
USB mass-storage
A flash drive, a typical USB mass-storage device.
USB implements connections to storage devices using a set of standards called the USB mass storage device class (referred to as MSC or UMS). This was initially intended for traditional magnetic and optical drives, but has been extended to support a wide variety of devices, particularly flash drives, which have replaced floppy disks for data transport. Though most computers are capable of booting off of USB Mass Storage devices, USB is not intended to be a primary bus for a computer's internal storage: buses such as ATA (IDE), Serial ATA (SATA), and SCSI fulfill that role.
However, USB has one important advantage in that it is possible to install and remove devices without opening the computer case, making it useful for external drives. Originally conceived and still used today for optical storage devices (CD-RW drives, DVD drives, etc.), a number of manufacturers offer external portable USB hard drives, or empty enclosures for drives, that offer performance comparable to internal drives. These external drives usually contain a translating device that interfaces a drive of conventional technology (IDE, ATA, SATA, ATAPI, or even SCSI) to a USB port. Functionally, the drive appears to the user just like another internal drive. Other competing standards that allow for external connectivity are eSATA and FireWire.
Human-interface devices (HIDs)
Mice and keyboards are frequently fitted with USB connectors, but because most PC motherboards still retain PS/2 connectors for the keyboard and mouse as of 2007, they are often supplied with a small USB-to-PS/2 adaptor, allowing usage with either USB or PS/2 interface. There is no logic inside these adaptors: they make use of the fact that such HID interfaces are equipped with controllers that are capable of serving both the USB and the PS/2 protocol, and automatically detect which type of port they are plugged in to. Joysticks, keypads, tablets and other human-interface devices are also progressively migrating from MIDI, PC game port, and PS/2 connectors to USB.
Apple Macintosh computers have been using USB exclusively for all wired mice and keyboards since January 1999.
USB signalling
USB supports three data rates:
· A Low Speed (1.1, 2.0) rate of 1.5 Mbit/s (187 kB/s) that is mostly used for Human Interface Devices (HID) such as keyboards, mice, and joysticks.
· A Full Speed (1.1, 2.0) rate of 12 Mbit/s (1.5 MB/s). Full Speed was the fastest rate before the USB 2.0 specification and many devices fall back to Full Speed. Full Speed devices divide the USB bandwidth between them in a first-come first-served basis and it is not uncommon to run out of bandwidth with several isochronous devices. All USB Hubs support Full Speed.
· A Hi-Speed (2.0) rate of 480 Mbit/s (60 MB/s).
Experimental data rate:
· A Super-Speed (3.0) rate of 4.8 Gbit/s (600 MB/s). The USB 3.0 specification will be released by Intel and its partners in mid 2008 according to early reports from CNET news. According to Intel, bus speeds will be 10 times faster than USB 2.0 due to the inclusion of a fiber optic link that works with traditional copper connectors. Products using the 3.0 specification are likely to arrive in 2009 or 2010.
USB signals are transmitted on a twisted pair data cable with 90Ω ±15% impedance,[6] labeled D+ and D−. These collectively use half-duplex differential signaling to combat the effects of electromagnetic noise on longer lines. D+ and D− usually operate together; they are not separate simplex connections. Transmitted signal levels are 0.0–0.3 volts for low and 2.8–3.6 volts for high in Full Speed and Low Speed modes, and +-400mV in High Speed (HS) mode. In FS mode the cable wires are not terminated, but the HS mode has termination of 45Ω to ground, or 90Ω differential to match the data cable impedance.
USB uses a special protocol to negotiate the High Speed mode called "chirping". In simplified terms, a device that is HS capable always connects as an FS device first, but after receiving a USB RESET (both D+ and D- are driven LOW by host) it tries to pull the D- line high. If the host (or hub) is also HS capable, it returns alternating signals on D- and D+ lines letting the device know that the tier will operate at High Speed.
Clock tolerance is 480.00 Mbit/s ±500ppm, 12.000 Mbit/s ±2500ppm, 1.50 Mbit/s ±15000ppm.
The USB standard uses the NRZI system to encode data, and uses "bit stuffing" by always injecting one artificial "zero" bit if the stream of data contains six consecutive "ones" before converting the bit stream to NRZI.
Though Hi-Speed devices are commonly referred to as "USB 2.0" and advertised as "up to 480 Mbit/s", not all USB 2.0 devices are Hi-Speed. The USB-IF certifies devices and provides licenses to use special marketing logos for either "Basic-Speed" (low and full) or Hi-Speed after passing a compliance test and paying a licensing fee. All devices are tested according to the latest spec, so recently-compliant Low-Speed devices are also 2.0 devices.
The actual throughput currently (2006) attained with real devices is about two thirds of the maximum theoretical bulk data transfer rate of 53.248 MB/s.[7] Typical hi-speed USB devices operate at lower speeds, often about 3 MB/s overall, sometimes up to 10-20 MB/s. The highest USB data transfer rate claimed by USB vendors is 40 MB/s.
USB connector properties
Series "A" plug and receptacle.
The connectors which the USB committee specified were designed to support a number of USB's underlying goals, and to reflect lessons learned from the varied menagerie of connectors then in service.
· The connectors are particularly cheap to manufacture.[citation needed]
Usability
· It is difficult to incorrectly attach a USB connector. Connectors cannot be plugged-in upside down, and it is clear from the appearance and kinesthetic sensation of making a connection when the plug and socket are correctly mated. However, it is not obvious at a glance to the inexperienced user (or to a user without sight of the installation) which way around the connector goes, so it is often necessary to try both ways.
· Only a moderate insertion/removal force is needed (by specification). USB cables and small USB devices are held in place by the gripping force from the receptacle (without the need for the screws, clips, or thumbturns that other connectors require). The force needed to make or break a connection is modest, allowing connections to be made in awkward circumstances or by those with motor disabilities.
· The connectors enforce the directed topology of a USB network. USB does not support cyclical networks, so the connectors from incompatible USB devices are themselves incompatible. Unlike other communications systems (e.g. RJ-45 cabling) gender-changers are almost never used, making it difficult to create a cyclic USB network.
USB extension cord
Safety
· The connectors are designed to be robust. Many previous connector designs were fragile, with pins or other delicate components prone to bending or breaking, even with the application of only very modest force. The electrical contacts in a USB connector are protected by an adjacent plastic tongue, and the entire connecting assembly is further protected by an enclosing metal sheath. As a result USB connectors can safely be handled, inserted, and removed, even by a small child. The encasing sheath and the tough molded plug body mean that a connector can be dropped, stepped upon, even crushed or struck, all without damage; a considerable degree of force is needed to significantly damage a USB connector.
· The connector construction always ensures that the external sheath on the plug contacts with its counterpart in the receptacle before the four connectors within are connected. This sheath is typically connected to the system ground, allowing otherwise damaging static charges to be safely discharged by this route (rather than via delicate electronic components). This means of enclosure also means that there is a (moderate) degree of protection from electromagnetic interference afforded to the USB signal while it travels through the mated connector pair (this is the only location when the otherwise twisted data pair must travel a distance in parallel). In addition, the power and common connections are made after the system ground but before the data connections. This type of staged make-break timing allows for safe hot-swapping and has long been common practice in the design of connectors in the aerospace industry.
Compatibility
· The USB standard specifies relatively low tolerances for compliant USB connectors, intending to minimize incompatibilities in connectors produced by different vendors (a goal that has been very successfully achieved). Unlike most other connector standards, the USB specification also defines limits to the size of a connecting device in the area around its plug. This was done to avoid circumstances where a device complies with the connector specification but its large size blocks adjacent ports. Compliant devices must either fit within the size restrictions or support a compliant extension cable which does.
· Two-way communication is also possible. In general, cables have only plugs, and hosts and devices have only receptacles: hosts having type-A receptacles and devices type-B. Type-A plugs only mate with type-A receptacles, and type-B with type-B. However, an extension to USB called USB On-The-Go allows a single port to act as either a host or a device — chosen by which end of the cable plugs into the socket on the unit. Even after the cable is hooked up and the units are talking, the two units may "swap" ends under program control. This facility targets units such as PDAs where the USB link might connect to a PC's host port as a device in one instance, yet connect as a host itself to a keyboard and mouse device in another instance.
Types of USB connectors
Type A (left) and Type BUSB Connectors
Different types of USB connectors from left to right• micro USB plug• mini USB plug• B-type plug• A-type receptacle• A-type plug
Pin configuration of the USB connectors Standard A/B
There are several types of USB connectors, and some have been added as the specification has progressed. The original USB specification detailed Standard-A and Standard-B plugs and receptacles. The first engineering change noticed to the USB 2.0 specification added Mini-B plugs and receptacles.
The Mini-B, Micro-A, Micro-B , and Micro-AB connectors are used for smaller devices such as PDAs, mobile phones or digital cameras. The Standard-A plug is approximately 4 by 12 mm, the Standard-B approximately 7 by 8 mm, and the Micro-A and Micro-B plugs approximately 2 by 7 mm.
Micro-USB is a further connector, that was announced by the USB-IF on January 4, 2007.[8] It is intended to replace the Mini-USB plugs used in many new smartphones and Personal digital assistants. This Micro-USB plug is rated for 10,000 connect-disconnect cycles. It is about half the height of the mini-USB connector, but features a similar width. In the Universal Serial Bus Micro-USB Cables and Connectors Specification, details have been laid down for Micro-A plugs, Micro-AB receptacles, and Micro-B plugs and receptacles, along with a Standard-A receptacle to Micro-A plug adapter.
Proprietary connectors and formats
Microsoft's original Xbox game console uses standard USB 1.1 signaling in its controllers and memory cards, but feature proprietary connectors and ports. Similarly, IBM UltraPort uses standard USB signaling, but via a proprietary connection format. American Power Conversion uses USB signaling and HID device class on its uninterruptible power supplies using 10P10C connectors. HTC, a company which makes Windows Mobile-based Communicators, has a proprietary connector called HTC ExtUSB, which combines mini-USB with audio input and output. Apple uses the standard connection format on its MacBook Air but allows it to deliver power beyond the 500 mA limit in order to make its MacBook Air Superdrive work without an external power supply. Nokia includes a USB connection as part of the Pop-Port connector on their mobile phones.
Cables
The maximum length of a standard USB cable is 5.0 meters (16.4 ft). The primary reason for this limit is the maximum allowed round-trip delay of about 1500 ns. If a USB device does not answer to host commands within the allowed time, the host considers the command to be lost. When USB device response time, delays from using the maximum number of hubs and delays from cables connecting the hubs, host and device are summed, the maximum delay caused by a single cable turns out to be 26 ns [9]. The USB 2.0 specification states that the cable delay must be less than 5.2 ns per meter, which means that maximum length USB cable is 5 meters long. However, this is also very close to the maximum possible length when using a standard copper cable.
Using USB devices over a greater length require hubs or active extension cables. Active extension cables are bus-powered hubs equipped with two maximum length standard USB cables. USB connections can be extended to 50 m (160 ft) over CAT5 or up to 10 km (6.2 mi) over fiber by using special USB extender products developed by various manufacturers.
In practice, some USB devices may work with longer cable runs than 5 meters, if the number of hubs between the host and the device is less than the maximum number allowed by the USB standard. However, using a longer cable lowers both the signal quality and the voltage provided by the USB bus below the specification tolerance limits. This may prevent USB devices from working properly or even from working at all.
Pin
Name
Cable colour
Description
1
VCC
Red
+5V
2
D−
White
Data −
3
D+
Green
Data +
4
GND
Black
Ground
Power
The USB specification provides a 5 V (volts) supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.75 V (5 V±5%) between the positive and negative bus power lines.[10] Initially, a device is only allowed to draw 100 mA. It may request more current from the upstream device in units of 2 mA up to a maximum of 500 mA.
If a bus-powered hub is used, the devices downstream may only use a total of four units — 400 mA (i.e. 2 watts) — of current. This limits compliant bus-powered hubs to 4 ports. The host operating system typically keeps track of the power requirements of the USB network and may warn the computer's operator when a given segment requires more power than is available.
On-The-Go and Battery Charging Specification both add new powering modes to the USB specification. The latter specification allows USB devices to draw up to 1.5 A from hubs and hosts that follow the Battery Charging Specification.
As of June 14, 2007, all new mobile phones applying for license in China are required to adopt the USB port as a power port.[11]
In September, 2007 the Open Mobile Terminal Platform --a forum dominated by operators but including manufacturers such as Nokia, Samsung, Motorola, Sony Ericsson and LG--announced that its members had agreed on micro-USB as the future common connector for mobile devices. [12][13]
Non-standard Devices
A number of USB devices require more power than is permitted by the specifications for a single port. This is a common requirement of external hard and optical disc drives and other devices with motors or lamps. Such devices can be used with the use of an external power supply of adequate rating, which is allowed by the standard, or by means of a dual inputs USB cable, one input of which is used for power and data transfer, the other solely for power, which makes the device a non-standard USB device. Some external hubs may, in practice, supply more power to USB devices than required by the specification but a standard compliant device may not depend on this.
Some non-standard USB devices use the 5 V power supply without participating in a proper USB network. These are usually referred to as USB decorations. The typical example is a USB-powered reading light; fans, mug heaters, battery chargers (particularly for mobile telephones) and even miniature vacuum cleaners are available. In most cases, these items contain no digitally based circuitry, and thus are not proper USB devices at all. This can cause problems with some computers — the USB specification requires that devices connect in a low-power mode (100 mA maximum) and state how much current they need, before switching, with the host's permission, into high-power mode.
In addition to limiting the total average power used by the device, the USB specification limits the inrush current (to charge decoupling and bulk capacitors) when the device is first connected; otherwise, connecting a device could cause glitches in the host's internal power. Also, USB devices are required to automatically enter ultra low-power suspend mode when the USB host is suspended; many USB hosts do not cut off the power supply to USB devices when they are suspended since resuming from the suspended state would become a lot more complicated if they did.
There are also devices at the host end that do not support negotiation, such as battery packs that can power USB powered devices; some provide power, while others pass through the data lines to a host PC. USB Power adapters convert utility power and/or power from a car's electrical system to run attached devices. Some of these devices can supply up to 1 A of current. Without negotiation, the powered USB device is unable to inquire if it is allowed to draw 100 mA, 500 mA, or 1 A.
PoweredUSB
Main article: PoweredUSB
PoweredUSB uses standard USB signaling with the addition of extra power lines. It uses 4 additional pins to supply up to 6A at either 5V, 12V, or 24V (depending on keying) to peripheral devices. The wires and contacts on the USB portion have been upgraded to support higher current on the 5V line, as well. This is commonly used in retail systems and provides enough power to operate stationary barcode scanners, printers, pin pads, signature capture devices, etc. This standard was developed by IBM, NCR, and FCI/Berg. It is essentially two connectors stacked such that the bottom connector accepts a standard USB plug and the top connector takes a power connector.
USB compared with FireWire
USB was originally seen as a complement to FireWire (IEEE 1394), which was designed as a high-speed serial bus which could efficiently interconnect peripherals such as hard disks, audio interfaces, and video equipment. USB originally operated at a far lower data rate and used much simpler hardware, and was suitable for small peripherals such as keyboards and mice.
The most significant technical differences between FireWire and USB include the following:
· USB networks use a tiered-star topology, while FireWire networks use a repeater-based topology.
· USB uses a "speak-when-spoken-to" protocol; peripherals cannot communicate with the host unless the host specifically requests communication. A FireWire device can communicate with any other node at any time, subject to network conditions.
· A USB network relies on a single host at the top of the tree to control the network. In a FireWire network, any capable node can control the network.
These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video. Although similar in theoretical maximum transfer rate, in real-world use, especially for high-bandwidth use such as external hard-drives, FireWire 400 generally has a significantly higher throughput than USB 2.0 Hi-Speed.[14][15][16][17] The newer FireWire 800 standard is twice as fast as FireWire 400 and outperforms USB 2.0 Hi-Speed both theoretically and practically.[18]
There are technical reasons why USB 2.0 devices cannot efficiently utilize all the available bandwidth. USB communication is based on polling the devices; there is no pipelining of commands. After sending a command to a device, the USB host must wait for a reply to the command before a new command can be sent to the same device. The bandwidth of a USB bus is divided by all devices connected to the bus. The USB host cannot send commands to one device while waiting for reply from another device. Since all communication is initiated by a USB host, the host must periodically poll all those USB devices that can provide data at unexpected intervals, such as network cards and keyboards. This consumes unnecessary resources when the devices are idle. These issues are being addressed by the forthcoming USB 3.0 specification, although it is not clear whether USB 3.0 is going to match FireWire in bandwidth efficiency.[19]
One reason USB supplanted Firewire, and became far more widespread, is cost; firewire is considerably more expensive to implement, producing more expensive hardware.
Version history
Prereleases
Hi-Speed USB Logo
USB OTG Logo
· USB 0.7: Released in November 1994.
· USB 0.8: Released in December 1994.
· USB 0.9: Released in April 1995.
· USB 0.99: Released in August 1995.
· USB 1.0 Release Candidate: Released in November 1995.
USB 1.0
· USB 1.0: Released in January 1996.Specified data rates of 1.5 Mbit/s (Low-Speed) and 12 Mbit/s (Full-Speed). Did not anticipate or pass-through monitors. Few such devices actually made it to market.
· USB 1.1: Released in September 1998.Fixed problems identified in 1.0, mostly relating to hubs. Earliest revision to be widely adopted.
USB 2.0
· USB 2.0: Released in April 2000.Added higher maximum speed of 480 Mbit/s (now called Hi-Speed). Further modifications to the USB specification have been done via Engineering Change Notices (ECN). The most important of these ECNs are included into the USB 2.0 specification package available from USB.org:
o Mini-B Connector ECN: Released in October 2000.Specifications for Mini-B plug and receptacle. These should not be confused with Micro-B plug and receptacle.
o Errata as of December 2000: Released in December 2000.
o Pull-up/Pull-down Resistors ECN: Released in May 2002.
o Errata as of May 2002: Released in May 2002.
o Interface Associations ECN: Released in May 2003.New standard descriptor was added that allows multiple interfaces to be associated with a single device function.
o Rounded Chamfer ECN: Released in October 2003.A recommended, compatible change to Mini-B plugs that results in longer lasting connectors.
o Unicode ECN: Released in February 2005.This ECN specifies that strings are encoded using UTF-16LE. USB 2.0 did specify that Unicode is to be used but it did not specify the encoding.
o Inter-Chip USB Supplement: Released in March 2006.
o On-The-Go Supplement 1.3: Released in December 2006.USB On-The-Go makes it possible for two USB devices to communicate with each other without requiring a separate USB host. In practice, one of the USB devices acts as a host for the other device.
o Battery Charging Specification 1.0: Released in March 2007.Adds support for dedicated chargers (power supplies with USB connectors), host chargers (USB hosts that can act as chargers) and the no Dead Battery Provision which allows devices to temporarily draw 100 mA current after they have been attached. If a USB device is connected to dedicated charger or host charger, maximum current drawn by the device may be as high as 1.5 A. (Note that this document is not distributed with USB 2.0 specification package.)
o Micro-USB Cables and Connectors Specification 1.01: Released in April 2007.
o Link Power Management Addendum ECN: Released in July 2007.This adds a new power state between enabled and suspended states. Device in this state is not required to reduce its power consumption. However, switching between enabled and sleep states is much faster than switching between enabled and suspended states, which allows devices to sleep while idle.
o High-Speed Inter-Chip USB Electrical Specification Revision 1.0: Released in September 2007.
USB 3.0
· USB 3.0 (Future version): On September 18, 2007, Pat Gelsinger demonstrated USB 3.0 at the fall Intel Developer Forum. USB 3.0 is targeted at ten times the current bandwidth, reaching roughly 5.0 Gbit/s by utilizing two additional high-speed differential pairs for "Superspeed" mode, and with the possibility for optical interconnect.[20] The USB 3.0 specification is planned to be released in the first half of 2008, commercial products are expected to arrive in 2009 or 2010.[21]
· Backwards-Compatibility and Efficiency: USB 3.0 is designed to be backwards-compatible with USB 2.0 and USB 1.1 and employs more efficient protocols to conserve power.[22]
Related technologies
The PictBridge standard allows for interconnecting consumer imaging devices. It typically uses USB as the underlying communication layer.
The USB Implementers Forum is working on a wireless networking standard based on the USB protocol. Wireless USB is intended as a cable-replacement technology, and will use ultra-wideband wireless technology for data rates of up to 480 Mbit/s. Wireless USB is well suited to wireless connection of PC centric devices, just as Bluetooth is now widely used for mobile phone centric personal networks (at much lower data rates).
Computer Processors
Microprocessor
A microprocessor incorporates the functions of a central processing unit (CPU) on a single integrated circuit (IC). [1] The first microprocessors used a word size of only 4 bits, so that the transistors of its logic circuits would fit onto a single part. One or more microprocessors typically serve as the processing elements of a computer system, embedded system, or handheld device. Microprocessors made possible the advent of the microcomputer in the mid-1970s. Before this period, CPUs were typically made from small-scale integrated circuits containing the equivalent of only a few transistors. By integrating the processor onto one or a very few large-scale integrated circuit packages (containing the equivalent of thousands or millions of discrete transistors), the cost of processing capacity was greatly reduced. Since the advent of the microprocessor in the mid 1970's, it has now become the most prevalent implementation of the CPU, almost completely replacing all other forms. See History of computing hardware for pre-electronic and early electronic computers.
Since the early 1970s, the increase in processing capacity of evolving microprocessors has been known to generally follow Moore's Law. It suggests that the complexity of an integrated circuit, with respect to minimum component cost, doubles every 18 months. In the early 1990s, microprocessor's heat generation (TDP) - due to current leakage - emerged as a leading developmental constraint[2]. From their humble beginnings as the drivers for calculators, the continued increase in processing capacity has led to the dominance of microprocessors over every other form of computer; every system from the largest mainframes to the smallest handheld computers now uses a microprocessor at its core.
Contents
[hide]
1 History
1.1 First types
1.2 Notable 8-bit designs
1.3 16-bit designs
1.4 32-bit designs
1.5 64-bit designs in personal computers
1.6 Multicore designs
1.7 RISC
2 Special-purpose designs
3 Market statistics
4 Architectures
5 See also
5.1 Major designers
6 References
7 External links
7.1 General
7.2 Historical documents
History
First types
The 4004 with cover removed (left) and as actually used (right).
Three projects arguably delivered a complete microprocessor at about the same time, namely Intel's 4004, the Texas Instruments (TI) TMS 1000, and Garrett AiResearch's Central Air Data Computer (CADC).
In 1968, Garrett AiResearch, with designer Ray Holt and Steve Geller, were invited to produce a digital computer to compete with electromechanical systems then under development for the main flight control computer in the US Navy's new F-14 Tomcat fighter. The design was complete by 1970, and used a MOS-based chipset as the core CPU. The design was significantly (approximately 20 times) smaller and much more reliable than the mechanical systems it competed against, and was used in all of the early Tomcat models. This system contained a "a 20-bit, pipelined, parallel multi-microprocessor". However, the system was considered so advanced that the Navy refused to allow publication of the design until 1997. For this reason the CADC, and the MP944 chipset it used, are fairly unknown even today. (see First Microprocessor Chip Set.) TI developed the 4-bit TMS 1000, and stressed pre-programmed embedded applications, introducing a version called the TMS1802NC on September 17, 1971, which implemented a calculator on a chip. The Intel chip was the 4-bit 4004, released on November 15, 1971, developed by Federico Faggin and Marcian Hoff.
TI filed for the patent on the microprocessor. Gary Boone was awarded U.S. Patent 3,757,306 for the single-chip microprocessor architecture on September 4, 1973. It may never be known which company actually had the first working microprocessor running on the lab bench. In both 1971 and 1976, Intel and TI entered into broad patent cross-licensing agreements, with Intel paying royalties to TI for the microprocessor patent. A nice history of these events is contained in court documentation from a legal dispute between Cyrix and Intel, with TI as intervenor and owner of the microprocessor patent.
Interestingly, a third party (Gilbert Hyatt) was awarded a patent which might cover the "microprocessor". See a webpage claiming an invention pre-dating both TI and Intel, describing a "microcontroller". According to a rebuttal and a commentary, the patent was later invalidated, but not before substantial royalties were paid out.
A computer-on-a-chip is a variation of a microprocessor which combines the microprocessor core (CPU), some memory, and I/O (input/output) lines, all on one chip. The computer-on-a-chip patent, called the "microcomputer patent" at the time, U.S. Patent 4,074,351 , was awarded to Gary Boone and Michael J. Cochran of TI. Aside from this patent, the standard meaning of microcomputer is a computer using one or more microprocessors as its CPU(s), while the concept defined in the patent is perhaps more akin to a microcontroller.
According to A History of Modern Computing, (MIT Press), pp. 220–21, Intel entered into a contract with Computer Terminals Corporation, later called Datapoint, of San Antonio TX, for a chip for a terminal they were designing. Datapoint later decided to use the chip, and Intel marketed it as the 8008 in April, 1972. This was the world's first 8-bit microprocessor. It was the basis for the famous "Mark-8" computer kit advertised in the magazine Radio-Electronics in 1974. The 8008 and its successor, the world-famous 8080, opened up the microprocessor component marketplace.
Notable 8-bit designs
The 4004 was later followed in 1972 by the 8008, the world's first 8-bit microprocessor. These processors are the precursors to the very successful Intel 8080 (1974), Zilog Z80 (1976), and derivative Intel 8-bit processors. The competing Motorola 6800 was released August 1974. Its architecture was cloned and improved in the MOS Technology 6502 in 1975, rivaling the Z80 in popularity during the 1980s.
Both the Z80 and 6502 concentrated on low overall cost, through a combination of small packaging, simple computer bus requirements, and the inclusion of circuitry that would normally have to be provided in a separate chip (for instance, the Z80 included a memory controller). It was these features that allowed the home computer "revolution" to take off in the early 1980s, eventually delivering such inexpensive machines as the Sinclair ZX-81, which sold for US$99.
The Western Design Center, Inc. (WDC) introduced the CMOS 65C02 in 1982 and licensed the design to several companies which became the core of the Apple IIc and IIe personal computers, medical implantable grade pacemakers and defibrilators, automotive, industrial and consumer devices.WDC pioneered the licensing of microprocessor technology which was later followed by ARM and other microprocessor Intellectual Property (IP) providers in the 1990’s.
Motorola trumped the entire 8-bit world by introducing the MC6809 in 1978, arguably one of the most powerful, orthogonal, and clean 8-bit microprocessor designs ever fielded – and also one of the most complex hard-wired logic designs that ever made it into production for any microprocessor. Microcoding replaced hardwired logic at about this point in time for all designs more powerful than the MC6809 – specifically because the design requirements were getting too complex for hardwired logic.
Another early 8-bit microprocessor was the Signetics 2650, which enjoyed a brief flurry of interest due to its innovative and powerful instruction set architecture.
A seminal microprocessor in the world of spaceflight was RCA's RCA 1802 (aka CDP1802, RCA COSMAC) (introduced in 1976) which was used in NASA's Voyager and Viking spaceprobes of the 1970s, and onboard the Galileo probe to Jupiter (launched 1989, arrived 1995). RCA COSMAC was the first to implement C-MOS technology. The CDP1802 was used because it could be run at very low power,* and because its production process (Silicon on Sapphire) ensured much better protection against cosmic radiation and electrostatic discharges than that of any other processor of the era. Thus, the 1802 is said to be the first radiation-hardened microprocessor.
16-bit designs
The first multi-chip 16-bit microprocessor was the National Semiconductor IMP-16, introduced in early 1973. An 8-bit version of the chipset was introduced in 1974 as the IMP-8. During the same year, National introduced the first 16-bit single-chip microprocessor, the National Semiconductor PACE, which was later followed by an NMOS version, the INS8900.
Other early multi-chip 16-bit microprocessors include one used by Digital Equipment Corporation (DEC) in the LSI-11 OEM board set and the packaged PDP 11/03 minicomputer, and the Fairchild Semiconductor MicroFlame 9440, both of which were introduced in the 1975 to 1976 timeframe.
The first single-chip 16-bit microprocessor was TI's TMS 9900, which was also compatible with their TI-990 line of minicomputers. The 9900 was used in the TI 990/4 minicomputer, the TI-99/4A home computer, and the TM990 line of OEM microcomputer boards. The chip was packaged in a large ceramic 64-pin DIP package, while most 8-bit microprocessors such as the Intel 8080 used the more common, smaller, and less expensive plastic 40-pin DIP. A follow-on chip, the TMS 9980, was designed to compete with the Intel 8080, had the full TI 990 16-bit instruction set, used a plastic 40-pin package, moved data 8 bits at a time, but could only address 16 KB. A third chip, the TMS 9995, was a new design. The family later expanded to include the 99105 and 99110.
The Western Design Center, Inc. (WDC) introduced the CMOS 65816 16-bit upgrade of the WDC CMOS 65C02 in 1984. The 65816 16-bit microprocessor was the core of the Apple IIgs and later the Super Nintendo Entertainment System, making it one of the most popular 16-bit designs of all time.
Intel followed a different path, having no minicomputers to emulate, and instead "upsized" their 8080 design into the 16-bit Intel 8086, the first member of the x86 family which powers most modern PC type computers. Intel introduced the 8086 as a cost effective way of porting software from the 8080 lines, and succeeded in winning much business on that premise. The 8088, a version of the 8086 that used an external 8-bit data bus, was the microprocessor in the first IBM PC, the model 5150. Following up their 8086 and 8088, Intel released the 80186, 80286 and, in 1985, the 32-bit 80386, cementing their PC market dominance with the processor family's backwards compatibility.
The integrated microprocessor memory management unit (MMU) was developed by Childs et al. of Intel, and awarded US patent number 4,442,484.
32-bit designs
Upper interconnect layers on an Intel 80486DX2 die.
16-bit designs were in the market only briefly when full 32-bit implementations started to appear.
The most significant of the 32-bit designs is the MC68000, introduced in 1979. The 68K, as it was widely known, had 32-bit registers but used 16-bit internal data paths, and a 16-bit external data bus to reduce pin count, and supported only 24-bit addresses. Motorola generally described it as a 16-bit processor, though it clearly has 32-bit architecture. The combination of high speed, large (16 megabytes (2^24)) memory space and fairly low costs made it the most popular CPU design of its class. The Apple Lisa and Macintosh designs made use of the 68000, as did a host of other designs in the mid-1980s, including the Atari ST and Commodore Amiga.
The world's first single-chip fully-32-bit microprocessor, with 32-bit data paths, 32-bit buses, and 32-bit addresses, was the AT&T Bell Labs BELLMAC-32A, with first samples in 1980, and general production in 1982 (See this bibliographic reference and this general reference). After the divestiture of AT&T in 1984, it was renamed the WE 32000 (WE for Western Electric), and had two follow-on generations, the WE 32100 and WE 32200. These microprocessors were used in the AT&T 3B5 and 3B15 minicomputers; in the 3B2, the world's first desktop supermicrocomputer; in the "Companion", the world's first 32-bit laptop computer; and in "Alexander", the world's first book-sized supermicrocomputer, featuring ROM-pack memory cartridges similar to today's gaming consoles. All these systems ran the UNIX System V operating system.
Intel's first 32-bit microprocessor was the iAPX 432, which was introduced in 1981 but was not a commercial success. It had an advanced capability-based object-oriented architecture, but poor performance compared to other competing architectures such as the Motorola 68000.
Motorola's success with the 68000 led to the MC68010, which added virtual memory support. The MC68020, introduced in 1985 added full 32-bit data and address busses. The 68020 became hugely popular in the Unix supermicrocomputer market, and many small companies (e.g., Altos, Charles River Data Systems) produced desktop-size systems. Following this with the MC68030, which added the MMU into the chip, the 68K family became the processor for everything that wasn't running DOS. The continued success led to the MC68040, which included an FPU for better math performance. A 68050 failed to achieve its performance goals and was not released, and the follow-up MC68060 was released into a market saturated by much faster RISC designs. The 68K family faded from the desktop in the early 1990s.
Other large companies designed the 68020 and follow-ons into embedded equipment. At one point, there were more 68020s in embedded equipment than there were Intel Pentiums in PCs (See this webpage for this embedded usage information). The ColdFire processor cores are derivatives of the venerable 68020.
During this time (early to mid 1980s), National Semiconductor introduced a very similar 16-bit pinout, 32-bit internal microprocessor called the NS 16032 (later renamed 32016), the full 32-bit version named the NS 32032, and a line of 32-bit industrial OEM microcomputers. By the mid-1980s, Sequent introduced the first symmetric multiprocessor (SMP) server-class computer using the NS 32032. This was one of the design's few wins, and it disappeared in the late 1980s.
The MIPS R2000 (1984) and R3000 (1989) were highly successful 32-bit RISC microprocessors. They were used in high-end workstations and servers by SGI, among others.
Other designs included the interesting Zilog Z8000, which arrived too late to market to stand a chance and disappeared quickly.
In the late 1980s, "microprocessor wars" started killing off some of the microprocessors. Apparently, with only one major design win, Sequent, the NS 32032 just faded out of existence, and Sequent switched to Intel microprocessors.
From 1985 to 2003, the 32-bit x86 architectures became increasingly dominant in desktop, laptop, and server markets, and these microprocessors became faster and more capable. Intel had licensed early versions of the architecture to other companies, but declined to license the Pentium, so AMD and Cyrix built later versions of the architecture based on their own designs. During this span, these processors increased in complexity (transistor count) and capability (instructions/second) by at least a factor of 1000. Intel's Pentium line is probably the most famous and recognizable 32-bit processor model, at least with the public at large.
64-bit designs in personal computers
While 64-bit microprocessor designs have been in use in several markets since the early 1990s, the early 2000s saw the introduction of 64-bit microchips targeted at the PC market.
With AMD's introduction of the first 64-bit IA-32 backwards-compatible architecture, AMD64, in September 2003, followed by Intel's own x86-64 chips, the 64-bit desktop era began. Both processors can run 32-bit legacy apps as well as the new 64-bit software. With 64-bit Windows XP, Windows Vista x64, Linux and Mac OS X (to a certain extent) that run 64-bit native, the software too is geared to utilize the full power of such processors. The move to 64 bits is more than just an increase in register size from the IA-32 as it also doubles the number of general-purpose registers for the aging CISC designs.
The move to 64 bits by PowerPC processors had been intended since the processors' design in the early 90s and was not a major cause of incompatibility. Existing integer registers are extended as are all related data pathways, but, as was the case with IA-32, both floating point and vector units had been operating at or above 64 bits for several years. Unlike what happened with IA-32 was extended to x86-64, no new general purpose registers were added in 64-bit PowerPC, so any performance gained when using the 64-bit mode for applications making no use of the larger address space is minimal.
Multicore designs
AMD Athlon 64 X2 3600 Dual core processor
Main article: Multi-core (computing)
A different approach to improving a computer's performance is to add extra processors, as in symmetric multiprocessing designs which have been popular in servers and workstations since the early 1990s. Keeping up with Moore's Law is becoming increasingly challenging as chip-making technologies approach the physical limits of the technology.
In response, the microprocessor manufacturers look for other ways to improve performance, in order to hold on to the momentum of constant upgrades in the market.
A multi-core processor is simply a single chip containing more than one microprocessor core, effectively multiplying the potential performance with the number of cores (as long as the operating system and software is designed to take advantage of more than one processor). Some components, such as bus interface and second level cache, may be shared between cores. Because the cores are physically very close they interface at much faster clock speeds compared to discrete multiprocessor systems, improving overall system performance.
In 2005, the first mass-market dual-core processors were announced and as of 2007 dual-core processors are widely used in servers, workstations and PCs while quad-core processors are now available for high-end applications in both the home and professional environments.
Sun Microsystems has released the Niagara and Niagara 2 chips, both of which feature an eight-core design. The Niagara 2 supports more threads and operates at 1.6 GHz.
RISC
In the mid-1980s to early-1990s, a crop of new high-performance RISC (reduced instruction set computer) microprocessors appeared, which were initially used in special purpose machines and Unix workstations, but then gained wide acceptance in other roles.
The first commercial design was released by MIPS Technologies, the 32-bit R2000 (the R1000 was not released). The R3000 made the design truly practical, and the R4000 introduced the world's first 64-bit design. Competing projects would result in the IBM POWER and Sun SPARC systems, respectively. Soon every major vendor was releasing a RISC design, including the AT&T CRISP, AMD 29000, Intel i860 and Intel i960, Motorola 88000, DEC Alpha and the HP-PA.
Market forces have "weeded out" many of these designs, with almost no desktop or laptop RISC processors and with the SPARC being used in Sun designs only. MIPS is primarily used in embedded systems, notably in Cisco routers. The rest of the original crop of designs have disappeared. Other companies have attacked niches in the market, notably ARM, originally intended for home computer use but since focussed at the embedded processor market. Today RISC designs based on the MIPS, ARM or PowerPC core power the vast majority of computing devices.
As of 2007, two 64-bit RISC architectures are still produced in volume: SPARC and Power Architecture. The RISC-like Itanium is produced in smaller quantities. The vast majority of 64-bit microprocessors are now x86-64 CISC designs from AMD and Intel.
Special-purpose designs
A 4-bit, 2 register, six assembly language instruction computer made entirely of 74-series chips.
Though the term "microprocessor" has traditionally referred to a single- or multi-chip CPU or system-on-a-chip (SoC), several types of specialized processing devices have followed from the technology. The most common examples are microcontrollers, digital signal processors (DSP) and graphics processing units (GPU). Many examples of these are either not programmable, or have limited programming facilities. For example, in general GPUs through the 1990s were mostly non-programmable and have only recently gained limited facilities like programmable vertex shaders. There is no universal consensus on what defines a "microprocessor", but it is usually safe to assume that the term refers to a general-purpose CPU of some sort and not a special-purpose processor unless specifically noted.
The RCA 1802 had what is called a static design, meaning that the clock frequency could be made arbitrarily low, even to 0 Hz, a total stop condition. This let the Voyager/Viking/Galileo spacecraft use minimum electric power for long uneventful stretches of a voyage. Timers and/or sensors would awaken/speed up the processor in time for important tasks, such as navigation updates, attitude control, data acquisition, and radio communication.
Market statistics
In 2003, about $44 billion (USD) worth of microprocessors were manufactured and sold. [1] Although about half of that money was spent on CPUs used in desktop or laptop personal computers, those count for only about 0.2% of all CPUs sold.
Silicon Valley has an old saying: "The first chip costs a million dollars; the second one costs a nickel." In other words, most of the cost is in the design and the manufacturing setup: once manufacturing is underway, it costs almost nothing.[citation needed]
About 55% of all CPUs sold in the world are 8-bit microcontrollers. Over 2 billion 8-bit microcontrollers were sold in 1997. [2]
Less than 10% of all the CPUs sold in the world are 32-bit or more. Of all the 32-bit CPUs sold, about 2% are used in desktop or laptop personal computers, the rest are sold in household appliances such as toasters, microwaves, vacuum cleaners and televisions. "Taken as a whole, the average price for a microprocessor, microcontroller, or DSP is just over $6." [3]
Architectures
65xx
MOS Technology 6502
Western Design Center 65xx
ARM family
Altera Nios, Nios II
Atmel AVR architecture (purely microcontrollers)
EISC
RCA 1802 (aka RCA COSMAC, CDP1802)
DEC Alpha
Intel
Intel 4004, 4040
Intel 8080, 8085, Zilog Z80
Intel Itanium
Intel i860
Intel i960
LatticeMico32
M32R architecture
MIPS architecture
Motorola
Motorola 6800
Motorola 6809
Motorola 68000 family, ColdFire
Motorola 88000 (parent of PowerPC family, with POWER)
IBM POWER, parent of PowerPC family, with 88000
PowerPC family, G3, G4, G5
NSC 320xx
OpenCores OpenRISC architecture
PA-RISC family
National Semiconductor SC/MP ("scamp")
Signetics 2650
SPARC
SuperH family
Transmeta Crusoe, Efficeon (VLIW architectures, IA-32 32-bit Intel x86 emulator)
INMOS Transputer
x86 architecture
Intel 8086, 8088, 80186, 80188 (16-bit real mode-only x86 architecture)
Intel 80286 (16-bit real mode and protected mode x86 architecture)
IA-32 32-bit x86 architecture
x86-64 64-bit x86 architecture
XAP processor from Cambridge Consultants
Xilinx
MicroBlaze soft processor
PowerPC405 embedded hard processor in Virtex FPGAs
3D Display
3D display
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A 3D display prototype by Philips
A 3D display is any display device capable of conveying three-dimensional images to the viewer.
There are many types of 3D displays: stereoscopic 3D displays show a different image to each eye; autostereoscopic 3D displays do this without the need for any special glasses or other head gear; holographic 3D displays reproduce a light field which is identical to that which emanated from the original scene. In addition there are volumetric displays, where some physical mechanism is used to display points of light within a volume. Such displays use voxels instead of pixels. Volumetric displays include multiplanar displays, which have multiple display planes stacked up; and rotating panel displays, where a rotating panel sweeps out a volume.
A wide range of organisations have developed 3D displays, ranging from experimental displays in university departments to commercially available displays. Companies involved include Holografika, NewSight, Pavonine, Philips, Spatial View, 3DIcon Corporation, Sharp, SeeReal Technologies and Alioscopy.
Computer Monitor / Display
Computer display
A computer display monitor, usually called simply a monitor, is a piece of electrical equipment which displays viewable images generated by a computer without producing a permanent record. The word "monitor" is used in other contexts; in particular in television broadcasting, where a television picture is displayed to a high standard. A computer display device is usually either a cathode ray tube or some form of flat panel such as a TFT LCD. The monitor comprises the display device, circuitry to generate a picture from electronic signals sent by the computer, and an enclosure or case. Within the computer, either as an integral part or a plugged-in interface, there is circuitry to convert internal data to a format compatible with a monitor.
Contents
[hide]
1 Screen Size
1.1 Diagonal size
1.2 Widescreen area
2 Imaging technologies
2.1 Cathode ray tube
3 Performance measurements
3.1 Comparison
3.1.1 CRT
3.1.2 Passive LCD
3.1.3 TFT LCD
3.1.4 Plasma
3.1.5 Penetron
4 Problems
4.1 Dead pixels
4.2 Stuck pixels
4.3 Phosphor burn-in
4.4 Plasma burn-in
4.5 Black level misadjustment
4.6 Glare
4.7 Color misregistration
4.8 Incomplete spectrum
5 Display interfaces
5.1 Computer Terminals
5.2 Composite signal
5.3 Digital monitors
5.3.1 TTL monitors
5.3.2 Single colour screens
6 Modern technology
6.1 Analog RGB monitors
6.2 Digital and analog combination
7 Configuration and usage
7.1 Multi-head
7.2 Virtual displays
8 Additional features
8.1 Power saving
8.2 Directional screen
8.3 Touch screen
9 Major manufacturers
10 See also
11 Interesting links
12 External links
Screen Size
Diagonal size
The inch size quoted is the diagonal size of the picture tube or LCD panel. With CRTs the picture is normally smaller by 1.5" - 2", hence a 17" LCD gives about the same size picture as a 19" CRT.
This method of size measurement dates from the early days of CRT television when round picture tubes were in common use, which only had one dimension that described display size. When rectangular tubes were used, the diagonal measurement of these was equivalent to the round tube's diameter, hence this was used (and of course it was the largest of the available numbers)
A better way to compare CRT and LCD displays is by viewable image size.
Widescreen area
A widescreen display always has less screen area for a given quoted inch size than a standard 4:3 display, due to basic geometry.
[edit] Imaging technologies
19" inch (48.3 cm tube, 45.9 cm viewable) CRT computer monitor
As with television, several different hardware technologies exist for displaying computer-generated output:
Liquid crystal display (LCD). TFT LCDs are the most popular display device for new computers in the Western world.
Passive LCD gives poor contrast and slow response, and other image defects. These were used in some laptops until the mid 1990s.
·
TFT Thin Film Transistor LCDs give much better picture quality in several respects. All modern LCD monitors are TFT.
Cathode ray tube (CRT)
Standard raster scan computer monitors
Vector displays, as used on the Vectrex, many scientific and radar applications, and several early arcade machines (notably Asteroids - always implemented using CRT displays due to requirement for a deflection system, though can be emulated on any raster-based display.
Television receivers were used by most early personal and home computers, connecting composite video to the television set using a modulator. Image quality was reduced by the additional steps of composite video ? modulator ? TV tuner ? composite video.
Plasma display
Surface-conduction electron-emitter display (SED)
Video projector - implemented using LCD, CRT, or other technologies. Recent consumer-level video projectors are almost exclusively LCD based.
Organic light-emitting diode (OLED) display
Penetron military aircraft displays
Cathode ray tube
CRT Computer display pixel array(right)
The CRT or cathode ray tube, is the picture tube of a monitor. The back of the tube has a negatively charged cathode. The electron gun shoots electrons down the tube and onto a charged screen. The screen is coated with a pattern of dots that glow when struck by the electron stream. Each cluster of three dots, one of each color, is one pixel.
The image on the monitor screen is usually made up from at least tens of thousands of such tiny dots glowing on command from the computer. The closer together the pixels are, the sharper the image on screen can be. The distance between pixels on a computer monitor screen is called its dot pitch and is measured in millimeters. Most monitors have a dot pitch of 0.28 mm or less.
There are two electromagnets around the collar of the tube which deflect the electron beam. The beam scans across the top of the monitor from left to right, is then blanked and moved back to the left-hand side slightly below the previous trace (on the next scan line), scans across the second line and so on until the bottom right of the screen is reached. The beam is again blanked, and moved back to the top left to start again. This process draws a complete picture, typically 50 to 100 times a second. The number of times in one second that the electron gun redraws the entire image is called the refresh rate and is measured in hertz (cycles per second). It is common, particularly in lower-priced equipment, for all the odd-numbered lines of an image to be traced, and then all the even-numbered lines; the circuitry of such an interlaced display need be capable of only half the speed of a non-interlaced display. An interlaced display, particularly at a relatively low refresh rate, can appear to some observers to flicker, and may cause eyestrain and nausea.
Performance measurements
The performance parameters of a monitor are:
Luminance, measured in candelas per square metre (cd/m²).
viewable image size, measured diagonally. For CRT the viewable size is one inch (25 mm) smaller then the tube itself.
Dot pitch. Describes the distance between pixels of the same color in millimetres. In general, the lower the dot pitch (e.g. 0.24 mm, which is also 240 micrometres), the sharper the picture will appear.
Response time. The amount of time a pixel in an LCD monitor takes to go from active (black) to inactive (white) and back to active (black) again. It is measured in milliseconds (ms). Lower numbers mean faster transitions and therefore fewer visible image artifacts.
Contrast ratio. The contrast ratio is defined as the ratio of the luminosity of the brightest color (white) to that of the darkest color (black) that the monitor is capable of producing.
Refresh rate. The number of times in a second that a display is illuminated.
Power consumption, measured in watts (W).
Aspect ratio, which is the horizontal size compared to the vertical size, e.g. 4:3 is the standard aspect ratio, so that a screen with a width of 1024 pixels will have a height of 768 pixels. A widescreen display can have an aspect ratio of 16:9, which means a display that is 1024 pixels wide will have a height of 576 pixels.
Display resolution. The number of distinct pixels in each dimension that can be displayed.
Comparison
CRT
High contrast ratio
High speed response
Full range light output level control
Large size
Large weight
Most produce geometric distortion
Greater power consumption than LCD.
Prone to moire effect at highest resolution
Can display natively in almost any resolution
Intolerant of damp conditions
Small risk of explosion if the picture tube glass is broken
Passive LCD
Very poor contrast ratio (eg 20:1)
High visible noise if used in more than 8 colour mode (3 bit colour depth).
Very slow response (moving images barely viewable)
Some suffer horizontal & vertical ghosting
Very small size
Very low weight
Very low power consumption
Lower cost than TFT LCDs.
Zero geometric distortion
TFT LCD
More or less all modern LCD monitors are the TFT type.
Medium contrast ratio
Response rates vary from one model to another, slower screens will show smearing on moving images
Very small size
Very low weight
Very low power consumption
Higher cost than Passive LCD or CRT.
Zero geometric distortion
LCDs of both types only have one native resolution. Displaying other resolutions requires conversion & interpolation, which often degrades image quality.
Plasma
High operating temperature can be painful to touch
Prone to burn-in
No geometric distortion
Highest cost option
High power consumption
Penetron
Main article: Penetron
Only found in military aircraft
2 colour display
See through
Orders of magnitude more expensive than the other display technologies listed here
Problems
Dead pixels
A fraction of all LCD monitors are produced with "dead pixels". Due to the desire for affordable monitors, most manufacturers sell monitors with dead pixels. Almost all manufacturers have clauses in their warranties which claim monitors with fewer than some number of dead pixels is not broken and will not be replaced. The dead pixels are usually stuck with the green, red, and/or blue subpixels either individually always stuck on or off.
Like image persistence, this can sometimes be partially or fully reversed by using the same method listed below, however the chance of success is far lower than with a "stuck" pixel. It can also sometimes be repaired by physically flicking the pixel, however it is always a possibility for someone to use too much force and rupture the weak screen internals doing this.
Stuck pixels
LCD monitors, while lacking phosphor screens and thus immune to phosphor burn-in, have a similar condition known as image persistence, where the pixels of the LCD monitor can "remember" a particular color and become "stuck" and unable to change. Unlike phosphor burn-in, however, image persistence can sometimes be reversed partially or completely.[citation needed] This is accomplished by rapidly displaying varying colors to "wake up" the stuck pixels.
Phosphor burn-in
Phosphor burn-in is localised aging of the phosphor layer of a CRT screen where it has displayed a static bright image for many years. This results in a faint permanent image on the screen, even when powered off. In severe cases it can even be possible to read some of the text, though this only occurs where the displayed text remained the same for years.
This was once a relatively common phenomenon in single purpose business computers. It can still be an issue with CRT displays when used to display the same image for years at a time, but modern computers aren't normally used this way any more, so the problem is not a significant issue today, with CRTs.
The size of the issue seems to have become exaggerated in popular opinion. The only systems that suffered the defect were ones displaying the same image for years, and with these the presence of burn-in was not a noticeable effect when in use, since it coincided with the displayed image perfectly. Also such systems were inevitably functional rather than eye candy, so even visible slight damage that occurred when reusing a heavily used business monitor for another business app was a trivial cosmetic issue. It only became a significant issue in 3 situations:
when some heavily used monitors were reused at home,
or re-used for display purposes
in some high security applications (but only those where the high security data displayed did not change for years at a time).
Screen savers were developed as a means to avoid burn-in, but are redundant for CRTs today, despite their popularity. The problem does not occur with multitasking systems, and powering down the display after a period of non-use is as effective and has additional benefits, such as increasing monitor life and reducing power use.
Phosphor Burn-in can be gradually removed on damaged CRT displays by displaying an all white screen with brightness & contrast turned up full. This is a slow procedure, and is usually but not always effective.
Plasma burn-in
Burn-in has re-emerged as an issue with plasma displays, which are much more vulnerable to this than CRTs. Screen savers with moving images may be used with these to minimise localised burn. Periodic change of the colour scheme in use also helps reduce the issue.
Black level misadjustment
User misadjustment of black level is common. This alters the colour displayed with most darker colours.
A testcard image may be used to set the image black level correctly. On CRT monitors
Black level is set with the 'brightness' control
White level is set with the 'contrast' control
sometimes black level can need readjustment after setting white level.
The naming of CRT controls is historic, and in some cases counterintuitive.
Glare
Glare is a problem caused by the relationship between lighting and screen, or by using monitors in bright sunlight. LCDs and flat screen CRTs are less prone to this than conventional curved CRTs, and trinitron CRTs, which are curved on one axis only, are less prone to it than other CRTs curved on both axes.
If the problem persists despite moving the monitor or adjusting lighting, a filter using a mesh of very fine black wires may be placed on the screen to reduce glare and improve contrast. These filters were popular in the late 1980s. They do also reduce light output, which can occasionally be an issue.
Color misregistration
With exceptions of DLP, most display technologies, especially LCD, have an inherent misregistration of the color channels, that is, the centres of the red, green, and blue dots do not line up perfectly. Subpixel rendering depends on this misalignment; technologies making use of this include the Apple II from 1976 [1], and more recently Microsoft (ClearType, 1998) and XFree86 (X Rendering Extension).
Incomplete spectrum
RGB displays produce most of the visible colour spectrum, but not all. This can be a problem where good colour matching to non-RGB images is needed. This issue is common to all monitor technologies with 3 colour channels.
Display interfaces
Computer Terminals
Early CRT-based VDUs (Visual Display Units) such as the DEC VT05 without graphics capabilities gained the label glass teletypes, because of the functional similarity to their electromechanical predecessors.
Some historic computers had no modern display, using a printer instead.
Composite signal
Early home computers such as the Apple II and the Commodore 64 used a composite signal output to drive a CRT monitor or TV. This resulted in degraded resolution due to compromises in the broadcast TV standards used. This method is still used with video game consoles.
Digital monitors
Early digital monitors are sometimes known as TTLs because the voltages on the red, green, and blue inputs are compatible with TTL logic chips. Later digital monitors support LVDS, or TMDS protocols.
TTL monitors
IBM PC with green monochrome display
An amber monochrome computer monitor, manufactured in 2007, which uses a 15-pin SVGA connector just like a standard color monitor.
Monitors used with the MDA, Hercules, CGA, and EGA graphics adapters used in early IBM PC's (Personal Computer) and clones were controlled via TTL logic. Such monitors can usually be identified by a male DB-9 connector used on the video cable. The disadvantage of TTL monitors was the limited number of colors available due to the low number of digital bits used for video signaling.
Modern monochrome monitors, such as the one pictured to the right which was manufactured in 2007, use the same 15-pin SVGA connector that standard color monitors use. They're capable of displaying 32-bit grayscale at 1024x768 resolution, making them able to interface and be used with modern computers.
TTL Monochrome monitors only made use of five out of the nine pins. One pin was used as a ground, and two pins were used for horizontal/vertical synchronization. The electron gun was controlled by two separate digital signals, a video bit, and an intensity bit to control the brightness of the drawn pixels. Only four unique shades were possible; black, dim, medium or bright.
CGA monitors used four digital signals to control the three electron guns used in color CRTs, in a signalling method known as RGBI, or Red Green and Blue, plus Intensity. Each of the three RGB colors can be switched on or off independently. The intensity bit increases the brightness of all guns that are switched on, or if no colors are switched on the intensity bit will switch on all guns at a very low brightness to produce a dark grey. A CGA monitor is only capable of rendering 16 unique colors. The CGA monitor was not exclusively used by PC based hardware. The Commodore 128 could also utilize CGA monitors. Many CGA monitors were capable of displaying composite video via a separate jack.
EGA monitors used six digital signals to control the three electron guns in a signalling method known as RrGgBb. Unlike CGA, each gun is allocated its own intensity bit. This allowed each of the three primary colors to have four different states (off, soft, medium, and bright) resulting in 64 possible colors.
Although not supported in the original IBM specification, many vendors of clone graphics adapters have implemented backwards monitor compatibility and auto detection. For example, EGA cards produced by Paradise could operate as a MDA, or CGA adapter if a monochrome or CGA monitor was used in place of an EGA monitor. Many CGA cards were also capable of operating as MDA or Hercules card if a monochrome monitor was used.
Single colour screens
Display colours other than white were very popular on monochrome monitors in the 1980s. These colours were more comfortable on the eye. This was particularly an issue at the time due to the lower refresh rates in use at the time causing flicker, plus the use of less comfortable colour schemes than used with most of today's software.
Green screens were the most popular colour, with orange displays also available. 'Paper white' was also in use, which was a warm white.
Modern technology
Analog RGB monitors
Most modern computer displays can show thousands or millions of different colors in the RGB color space by varying red, green, and blue signals in continuously variable intensities.
Digital and analog combination
Many monitors have analog signal relay, but some more recent models (mostly LCD screens) support digital input signals. It is a common misconception that all computer monitors are digital. For several years, televisions, composite monitors, and computer displays have been significantly different. However, as TVs have become more versatile, the distinction has blurred.
Configuration and usage
Multi-head
Main article: Multi-monitor
Some users use more than one monitor. The displays can operate in multiple modes. One of the most common spreads the entire desktop over all of the monitors, which thus act as one big desktop. The X Window System refers to this as Xinerama.
Two Apple flat-screen monitors used as dual display
Terminology:
Dualhead - Using two monitors
Triplehead - using three monitors
Display assembly - multi-head configurations actively managed as a single unit
Virtual displays
The X Window System provides configuration mechanisms for using a single hardware monitor for rendering multiple virtual displays, as controlled (for example) with the Unix DISPLAY global variable or with the -display command option.
Additional features
Power saving
More or less all modern monitors contain a power saving mode they will switch to if they receive no video input signal. Modern operating systems can thus power down a monitor after a specified period of inactivity. Typical lifetime cost savings outweight the cost of implementation. This also extends the service life of the monitor.
Some monitors will also switch themselves completely off after a time period on standby.
Some laptops have a dimmed screen mode they can use to extend battery life.] Directional screen
Narrow viewing angle screens are used in some security conscious applications.] Touch screen
These monitors use touching of the screen as an input method. Items can be selected or moved with a finger, and finger gestures may be used to convey commands. This does however mean the screen needs frequent cleaning due to image degradation from fingerprints.
Major manufacturers
Acer
Apple Inc.
BenQ
Dell, Inc.
Hewlett-Packard
Eizo
HannStar Display Corporation
Iiyama Corporation
LaCie
LG Electronics
NEC Display Solutions
Philips
Samsung
Sharp
Sony
ViewSonic
Westinghouse
Computer Monitor / Display
Computer display
A computer display monitor, usually called simply a monitor, is a piece of electrical equipment which displays viewable images generated by a computer without producing a permanent record. The word "monitor" is used in other contexts; in particular in television broadcasting, where a television picture is displayed to a high standard. A computer display device is usually either a cathode ray tube or some form of flat panel such as a TFT LCD. The monitor comprises the display device, circuitry to generate a picture from electronic signals sent by the computer, and an enclosure or case. Within the computer, either as an integral part or a plugged-in interface, there is circuitry to convert internal data to a format compatible with a monitor.
Contents
[hide]
1 Screen Size
1.1 Diagonal size
1.2 Widescreen area
2 Imaging technologies
2.1 Cathode ray tube
3 Performance measurements
3.1 Comparison
3.1.1 CRT
3.1.2 Passive LCD
3.1.3 TFT LCD
3.1.4 Plasma
3.1.5 Penetron
4 Problems
4.1 Dead pixels
4.2 Stuck pixels
4.3 Phosphor burn-in
4.4 Plasma burn-in
4.5 Black level misadjustment
4.6 Glare
4.7 Color misregistration
4.8 Incomplete spectrum
5 Display interfaces
5.1 Computer Terminals
5.2 Composite signal
5.3 Digital monitors
5.3.1 TTL monitors
5.3.2 Single colour screens
6 Modern technology
6.1 Analog RGB monitors
6.2 Digital and analog combination
7 Configuration and usage
7.1 Multi-head
7.2 Virtual displays
8 Additional features
8.1 Power saving
8.2 Directional screen
8.3 Touch screen
9 Major manufacturers
10 See also
11 Interesting links
12 External links
Screen Size
Diagonal size
The inch size quoted is the diagonal size of the picture tube or LCD panel. With CRTs the picture is normally smaller by 1.5" - 2", hence a 17" LCD gives about the same size picture as a 19" CRT.
This method of size measurement dates from the early days of CRT television when round picture tubes were in common use, which only had one dimension that described display size. When rectangular tubes were used, the diagonal measurement of these was equivalent to the round tube's diameter, hence this was used (and of course it was the largest of the available numbers)
A better way to compare CRT and LCD displays is by viewable image size.
Widescreen area
A widescreen display always has less screen area for a given quoted inch size than a standard 4:3 display, due to basic geometry.
[edit] Imaging technologies
19" inch (48.3 cm tube, 45.9 cm viewable) CRT computer monitor
As with television, several different hardware technologies exist for displaying computer-generated output:
Liquid crystal display (LCD). TFT LCDs are the most popular display device for new computers in the Western world.
Passive LCD gives poor contrast and slow response, and other image defects. These were used in some laptops until the mid 1990s.
·
TFT Thin Film Transistor LCDs give much better picture quality in several respects. All modern LCD monitors are TFT.
Cathode ray tube (CRT)
Standard raster scan computer monitors
Vector displays, as used on the Vectrex, many scientific and radar applications, and several early arcade machines (notably Asteroids - always implemented using CRT displays due to requirement for a deflection system, though can be emulated on any raster-based display.
Television receivers were used by most early personal and home computers, connecting composite video to the television set using a modulator. Image quality was reduced by the additional steps of composite video ? modulator ? TV tuner ? composite video.
Plasma display
Surface-conduction electron-emitter display (SED)
Video projector - implemented using LCD, CRT, or other technologies. Recent consumer-level video projectors are almost exclusively LCD based.
Organic light-emitting diode (OLED) display
Penetron military aircraft displays
Cathode ray tube
CRT Computer display pixel array(right)
The CRT or cathode ray tube, is the picture tube of a monitor. The back of the tube has a negatively charged cathode. The electron gun shoots electrons down the tube and onto a charged screen. The screen is coated with a pattern of dots that glow when struck by the electron stream. Each cluster of three dots, one of each color, is one pixel.
The image on the monitor screen is usually made up from at least tens of thousands of such tiny dots glowing on command from the computer. The closer together the pixels are, the sharper the image on screen can be. The distance between pixels on a computer monitor screen is called its dot pitch and is measured in millimeters. Most monitors have a dot pitch of 0.28 mm or less.
There are two electromagnets around the collar of the tube which deflect the electron beam. The beam scans across the top of the monitor from left to right, is then blanked and moved back to the left-hand side slightly below the previous trace (on the next scan line), scans across the second line and so on until the bottom right of the screen is reached. The beam is again blanked, and moved back to the top left to start again. This process draws a complete picture, typically 50 to 100 times a second. The number of times in one second that the electron gun redraws the entire image is called the refresh rate and is measured in hertz (cycles per second). It is common, particularly in lower-priced equipment, for all the odd-numbered lines of an image to be traced, and then all the even-numbered lines; the circuitry of such an interlaced display need be capable of only half the speed of a non-interlaced display. An interlaced display, particularly at a relatively low refresh rate, can appear to some observers to flicker, and may cause eyestrain and nausea.
Performance measurements
The performance parameters of a monitor are:
Luminance, measured in candelas per square metre (cd/m²).
viewable image size, measured diagonally. For CRT the viewable size is one inch (25 mm) smaller then the tube itself.
Dot pitch. Describes the distance between pixels of the same color in millimetres. In general, the lower the dot pitch (e.g. 0.24 mm, which is also 240 micrometres), the sharper the picture will appear.
Response time. The amount of time a pixel in an LCD monitor takes to go from active (black) to inactive (white) and back to active (black) again. It is measured in milliseconds (ms). Lower numbers mean faster transitions and therefore fewer visible image artifacts.
Contrast ratio. The contrast ratio is defined as the ratio of the luminosity of the brightest color (white) to that of the darkest color (black) that the monitor is capable of producing.
Refresh rate. The number of times in a second that a display is illuminated.
Power consumption, measured in watts (W).
Aspect ratio, which is the horizontal size compared to the vertical size, e.g. 4:3 is the standard aspect ratio, so that a screen with a width of 1024 pixels will have a height of 768 pixels. A widescreen display can have an aspect ratio of 16:9, which means a display that is 1024 pixels wide will have a height of 576 pixels.
Display resolution. The number of distinct pixels in each dimension that can be displayed.
Comparison
CRT
High contrast ratio
High speed response
Full range light output level control
Large size
Large weight
Most produce geometric distortion
Greater power consumption than LCD.
Prone to moire effect at highest resolution
Can display natively in almost any resolution
Intolerant of damp conditions
Small risk of explosion if the picture tube glass is broken
Passive LCD
Very poor contrast ratio (eg 20:1)
High visible noise if used in more than 8 colour mode (3 bit colour depth).
Very slow response (moving images barely viewable)
Some suffer horizontal & vertical ghosting
Very small size
Very low weight
Very low power consumption
Lower cost than TFT LCDs.
Zero geometric distortion
TFT LCD
More or less all modern LCD monitors are the TFT type.
Medium contrast ratio
Response rates vary from one model to another, slower screens will show smearing on moving images
Very small size
Very low weight
Very low power consumption
Higher cost than Passive LCD or CRT.
Zero geometric distortion
LCDs of both types only have one native resolution. Displaying other resolutions requires conversion & interpolation, which often degrades image quality.
Plasma
High operating temperature can be painful to touch
Prone to burn-in
No geometric distortion
Highest cost option
High power consumption
Penetron
Main article: Penetron
Only found in military aircraft
2 colour display
See through
Orders of magnitude more expensive than the other display technologies listed here
Problems
Dead pixels
A fraction of all LCD monitors are produced with "dead pixels". Due to the desire for affordable monitors, most manufacturers sell monitors with dead pixels. Almost all manufacturers have clauses in their warranties which claim monitors with fewer than some number of dead pixels is not broken and will not be replaced. The dead pixels are usually stuck with the green, red, and/or blue subpixels either individually always stuck on or off.
Like image persistence, this can sometimes be partially or fully reversed by using the same method listed below, however the chance of success is far lower than with a "stuck" pixel. It can also sometimes be repaired by physically flicking the pixel, however it is always a possibility for someone to use too much force and rupture the weak screen internals doing this.
Stuck pixels
LCD monitors, while lacking phosphor screens and thus immune to phosphor burn-in, have a similar condition known as image persistence, where the pixels of the LCD monitor can "remember" a particular color and become "stuck" and unable to change. Unlike phosphor burn-in, however, image persistence can sometimes be reversed partially or completely.[citation needed] This is accomplished by rapidly displaying varying colors to "wake up" the stuck pixels.
Phosphor burn-in
Phosphor burn-in is localised aging of the phosphor layer of a CRT screen where it has displayed a static bright image for many years. This results in a faint permanent image on the screen, even when powered off. In severe cases it can even be possible to read some of the text, though this only occurs where the displayed text remained the same for years.
This was once a relatively common phenomenon in single purpose business computers. It can still be an issue with CRT displays when used to display the same image for years at a time, but modern computers aren't normally used this way any more, so the problem is not a significant issue today, with CRTs.
The size of the issue seems to have become exaggerated in popular opinion. The only systems that suffered the defect were ones displaying the same image for years, and with these the presence of burn-in was not a noticeable effect when in use, since it coincided with the displayed image perfectly. Also such systems were inevitably functional rather than eye candy, so even visible slight damage that occurred when reusing a heavily used business monitor for another business app was a trivial cosmetic issue. It only became a significant issue in 3 situations:
when some heavily used monitors were reused at home,
or re-used for display purposes
in some high security applications (but only those where the high security data displayed did not change for years at a time).
Screen savers were developed as a means to avoid burn-in, but are redundant for CRTs today, despite their popularity. The problem does not occur with multitasking systems, and powering down the display after a period of non-use is as effective and has additional benefits, such as increasing monitor life and reducing power use.
Phosphor Burn-in can be gradually removed on damaged CRT displays by displaying an all white screen with brightness & contrast turned up full. This is a slow procedure, and is usually but not always effective.
Plasma burn-in
Burn-in has re-emerged as an issue with plasma displays, which are much more vulnerable to this than CRTs. Screen savers with moving images may be used with these to minimise localised burn. Periodic change of the colour scheme in use also helps reduce the issue.
Black level misadjustment
User misadjustment of black level is common. This alters the colour displayed with most darker colours.
A testcard image may be used to set the image black level correctly. On CRT monitors
Black level is set with the 'brightness' control
White level is set with the 'contrast' control
sometimes black level can need readjustment after setting white level.
The naming of CRT controls is historic, and in some cases counterintuitive.
Glare
Glare is a problem caused by the relationship between lighting and screen, or by using monitors in bright sunlight. LCDs and flat screen CRTs are less prone to this than conventional curved CRTs, and trinitron CRTs, which are curved on one axis only, are less prone to it than other CRTs curved on both axes.
If the problem persists despite moving the monitor or adjusting lighting, a filter using a mesh of very fine black wires may be placed on the screen to reduce glare and improve contrast. These filters were popular in the late 1980s. They do also reduce light output, which can occasionally be an issue.
Color misregistration
With exceptions of DLP, most display technologies, especially LCD, have an inherent misregistration of the color channels, that is, the centres of the red, green, and blue dots do not line up perfectly. Subpixel rendering depends on this misalignment; technologies making use of this include the Apple II from 1976 [1], and more recently Microsoft (ClearType, 1998) and XFree86 (X Rendering Extension).
Incomplete spectrum
RGB displays produce most of the visible colour spectrum, but not all. This can be a problem where good colour matching to non-RGB images is needed. This issue is common to all monitor technologies with 3 colour channels.
Display interfaces
Computer Terminals
Early CRT-based VDUs (Visual Display Units) such as the DEC VT05 without graphics capabilities gained the label glass teletypes, because of the functional similarity to their electromechanical predecessors.
Some historic computers had no modern display, using a printer instead.
Composite signal
Early home computers such as the Apple II and the Commodore 64 used a composite signal output to drive a CRT monitor or TV. This resulted in degraded resolution due to compromises in the broadcast TV standards used. This method is still used with video game consoles.
Digital monitors
Early digital monitors are sometimes known as TTLs because the voltages on the red, green, and blue inputs are compatible with TTL logic chips. Later digital monitors support LVDS, or TMDS protocols.
TTL monitors
IBM PC with green monochrome display
An amber monochrome computer monitor, manufactured in 2007, which uses a 15-pin SVGA connector just like a standard color monitor.
Monitors used with the MDA, Hercules, CGA, and EGA graphics adapters used in early IBM PC's (Personal Computer) and clones were controlled via TTL logic. Such monitors can usually be identified by a male DB-9 connector used on the video cable. The disadvantage of TTL monitors was the limited number of colors available due to the low number of digital bits used for video signaling.
Modern monochrome monitors, such as the one pictured to the right which was manufactured in 2007, use the same 15-pin SVGA connector that standard color monitors use. They're capable of displaying 32-bit grayscale at 1024x768 resolution, making them able to interface and be used with modern computers.
TTL Monochrome monitors only made use of five out of the nine pins. One pin was used as a ground, and two pins were used for horizontal/vertical synchronization. The electron gun was controlled by two separate digital signals, a video bit, and an intensity bit to control the brightness of the drawn pixels. Only four unique shades were possible; black, dim, medium or bright.
CGA monitors used four digital signals to control the three electron guns used in color CRTs, in a signalling method known as RGBI, or Red Green and Blue, plus Intensity. Each of the three RGB colors can be switched on or off independently. The intensity bit increases the brightness of all guns that are switched on, or if no colors are switched on the intensity bit will switch on all guns at a very low brightness to produce a dark grey. A CGA monitor is only capable of rendering 16 unique colors. The CGA monitor was not exclusively used by PC based hardware. The Commodore 128 could also utilize CGA monitors. Many CGA monitors were capable of displaying composite video via a separate jack.
EGA monitors used six digital signals to control the three electron guns in a signalling method known as RrGgBb. Unlike CGA, each gun is allocated its own intensity bit. This allowed each of the three primary colors to have four different states (off, soft, medium, and bright) resulting in 64 possible colors.
Although not supported in the original IBM specification, many vendors of clone graphics adapters have implemented backwards monitor compatibility and auto detection. For example, EGA cards produced by Paradise could operate as a MDA, or CGA adapter if a monochrome or CGA monitor was used in place of an EGA monitor. Many CGA cards were also capable of operating as MDA or Hercules card if a monochrome monitor was used.
Single colour screens
Display colours other than white were very popular on monochrome monitors in the 1980s. These colours were more comfortable on the eye. This was particularly an issue at the time due to the lower refresh rates in use at the time causing flicker, plus the use of less comfortable colour schemes than used with most of today's software.
Green screens were the most popular colour, with orange displays also available. 'Paper white' was also in use, which was a warm white.
Modern technology
Analog RGB monitors
Most modern computer displays can show thousands or millions of different colors in the RGB color space by varying red, green, and blue signals in continuously variable intensities.
Digital and analog combination
Many monitors have analog signal relay, but some more recent models (mostly LCD screens) support digital input signals. It is a common misconception that all computer monitors are digital. For several years, televisions, composite monitors, and computer displays have been significantly different. However, as TVs have become more versatile, the distinction has blurred.
Configuration and usage
Multi-head
Main article: Multi-monitor
Some users use more than one monitor. The displays can operate in multiple modes. One of the most common spreads the entire desktop over all of the monitors, which thus act as one big desktop. The X Window System refers to this as Xinerama.
Two Apple flat-screen monitors used as dual display
Terminology:
Dualhead - Using two monitors
Triplehead - using three monitors
Display assembly - multi-head configurations actively managed as a single unit
Virtual displays
The X Window System provides configuration mechanisms for using a single hardware monitor for rendering multiple virtual displays, as controlled (for example) with the Unix DISPLAY global variable or with the -display command option.
Additional features
Power saving
More or less all modern monitors contain a power saving mode they will switch to if they receive no video input signal. Modern operating systems can thus power down a monitor after a specified period of inactivity. Typical lifetime cost savings outweight the cost of implementation. This also extends the service life of the monitor.
Some monitors will also switch themselves completely off after a time period on standby.
Some laptops have a dimmed screen mode they can use to extend battery life.] Directional screen
Narrow viewing angle screens are used in some security conscious applications.] Touch screen
These monitors use touching of the screen as an input method. Items can be selected or moved with a finger, and finger gestures may be used to convey commands. This does however mean the screen needs frequent cleaning due to image degradation from fingerprints.
Major manufacturers
Acer
Apple Inc.
BenQ
Dell, Inc.
Hewlett-Packard
Eizo
HannStar Display Corporation
Iiyama Corporation
LaCie
LG Electronics
NEC Display Solutions
Philips
Samsung
Sharp
Sony
ViewSonic
Westinghouse
Evolution of Computers (Computer's History)
Random access memory
“RAM" redirects here. For other uses of the word, see Ram.
Example of writable but volatile random access memory: Dynamic RAM modules, primarily used as main memory in Personal computers
Random access memory (usually known by its acronym, RAM) is a type of computer data storage. It today takes the form of integrated circuits that allow the stored data to be accessed in any order, i.e. at random. The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.[1]
This contrasts with storage mechanisms such as tapes, magnetic discs and optical discs, which rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than the data transfer, and the retrieval time varies depending on the physical location of the next item.
The word RAM is mostly associated with volatile types of memory, where the information is lost when power is switched off. However, many other types of memory are RAM as well (i.e. Random Access Memory), including most types of ROM and a kind of flash memory called NOR-Flash.
Contents
[hide]
1 History
2 Overview
2.1 Types of RAM
2.2 Memory hierarchy
2.2.1 Swapping
2.3 Other uses of the term
2.3.1 "RAM disks"
3 Recent developments
4 Memory wall
5 See also
6 Terminology
7 Notes and references
8 External links
History
The first type of random access memory was the magnetic core memory, developed in 1951, and used in all computers up until the development of the static and dynamic RAM integrated circuits in the late 1960s and early 1970s. Prior to the development of the magnetic core memory computers used relays or vacuum tubes to perform memory functions.
Overview
Types of RAM
Modern types of writable RAM generally store a bit of data in either the state of a flip-flop, as in SRAM (static RAM), or as a charge in a capacitor (or transistor gate), as in DRAM (dynamic RAM), EPROM, EEPROM and Flash. Some types have circuitry to detect and/or correct random faults called memory errors in the stored data, using parity bits or error correction codes. RAM of the read-only type, ROM, instead uses a metal mask to permanently enable/disable selected transistors, instead of storing a charge in them.
As both SRAM and DRAM are volatile, other forms of computer storage, such as disks and magnetic tapes, have been used as "permanent" storage in traditional computers. Many newer products such as PDAs and small music players (up to 160 GB in Jan 2008) do not have hard disks, but often rely on flash memory to maintain data between sessions of use; the same can be said about products such as mobile phones, advanced calculators, synthesizers etc; even certain categories of personal computers have begun replacing magnetic disk with flash drives, such as the OLPC XO-1. There are two basic types of flash memory: the NOR type, which is capable of true random access, and the NAND type, which is not; the former is therefore often used in place of ROM, while the latter is used in most memory cards and solid-state drives, due to a lower price.
Memory hierarchy
1 Module of 128Mb NEC SD-RAM
Many computer systems have a memory hierarchy consisting of CPU registers, on-die SRAM caches, external caches, DRAM, paging systems, and virtual memory or swap space on a hard drive. This entire pool of memory may be referred to as "RAM" by many developers, even though the various subsystems can have very different access times, violating the original concept behind the random access term in RAM. Even within a hierarchy level such as DRAM, the specific row, column, bank, rank, channel, or interleave organization of the components make the access time variable, although not to the extent that rotating storage media or a tape is variable. (Generally, the memory hierarchy follows the access time with the fast CPU registers at the top and the slow hard drive at the bottom.)
In most modern personal computers, the RAM comes in easily upgraded form of modules called memory modules or DRAM modules about the size of a few sticks of chewing gum. These can quickly be replaced should they become damaged or too small for current purposes. As suggested above, smaller amounts of RAM (mostly SRAM) are also integrated in the CPU and other ICs on the motherboard, as well as in hard-drives, CD-ROMs, and several other parts of the computer system.
Swapping
If a computer becomes low on RAM during intensive application cycles, the computer can resort to swapping. In this case, the computer temporarily uses hard drive space as additional memory. Constantly relying on this type of backup memory is called thrashing, which is generally undesirable because it lowers overall system performance. In order to reduce the dependency on swapping, more RAM can be installed.
Other uses of the term
Other physical devices with read/write capability can have "RAM" in their names: for example, DVD-RAM. "Random access" is also the name of an indexing method: hence, disk storage is often called "random access" because the reading head can move relatively quickly from one piece of data to another, and does not have to read all the data in between. However the final "M" is crucial: "RAM" (provided there is no additional term as in "DVD-RAM") always refers to a solid-state device.
"RAM disks"
Software can "partition" a portion of a computer's RAM, allowing it to act as a much faster hard drive that is called a RAM disk. Unless the memory used is non-volatile, a RAM disk loses the stored data when the computer is shut down. However, volatile memory can retain its data when the computer is shut down if it has a separate power source, usually a battery.
Recent developments
Several new types of non-volatile RAM, which will preserve data while powered down, are under development. The technologies used include carbon nanotubes and the magnetic tunnel effect. In summer 2003, a 128 KB magnetic RAM chip manufactured with 0.18 µm technology was introduced. The core technology of MRAM is based on the magnetic tunnel effect. In June 2004, Infineon Technologies unveiled a 16 MB prototype again based on 0.18 µm technology. Nantero built a functioning carbon nanotube memory prototype 10 GB array in 2004. Whether some of these technologies will be able to eventually take a significant market share from either DRAM, SRAM, or flash-memory technology, remains to be seen however.
In 2006, "Solid-state drives" (based on flash memory) with capacities exceeding 150 gigabytes and speeds far exceeding traditional disks have become available. This development has started to blur the definition between traditional random access memory and "disks", dramatically reducing the difference in performance
Memory wall
The "memory wall" is the growing disparity of speed between CPU and memory outside the CPU chip. An important reason for this disparity is the limited communication bandwidth beyond chip boundaries. From 1986 to 2000, CPU speed improved at an annual rate of 55% while memory speed only improved at 10%. Given these trends, it was expected that memory latency would become an overwhelming bottleneck in computer performance. [2]
Currently, CPU speed improvements have slowed significantly partly due to major physical barriers and partly because current CPU designs have already hit the memory wall in some sense. Intel summarized these causes in their Platform 2015 documentation (PDF):
“First of all, as chip geometries shrink and clock frequencies rise, the transistor leakage current increases, leading to excess power consumption and heat (more on power consumption below). Secondly, the advantages of higher clock speeds are in part negated by memory latency, since memory access times have not been able to keep pace with increasing clock frequencies. Third, for certain applications, traditional serial architectures are becoming less efficient as processors get faster (due to the so-called Von Neumann bottleneck), further undercutting any – gains that frequency increases might otherwise buy. In addition, partly due to limitations in the means of producing inductance within solid state devices, resistance-capacitance (RC) delays in signal transmission are growing as feature sizes shrink, imposing an additional bottleneck that frequency increases don't address.”
The RC delays in signal transmission were also noted in Clock Rate versus IPC: The End of the Road for Conventional Microarchitectures which projects a maximum of 12.5% average annual CPU performance improvement between 2000 and 2014. The data on Intel Processors clearly shows a slowdown in performance improvements in recent processors. However, Intel's new processors, Core 2 Duo (codenamed Conroe) show a significant improvement over previous Pentium 4 processors; due to a more efficient architecture, performance increased while clock rate actually decreased.
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The Computer Tricks
Try this......
Just follow the following steps:
1.Select any file or folder.
2.Right click on it,press rename or simply press F2.
3.Press and hold the alt key.While holding the Alt key,type numbers 0160 from the numpad.
Note:Type the numbers 0160 from the numpad,that is,the numbers present on the right side of the keyboard.Dont type the numbers which are present on top of the character keys.
4.Press Enter and the nameless file or folder will be created.Reason:The file or folder that seems nameless is actually named with a single space.But what if you want to create another nameless file or folder in the same directory ?
For this you will have to rename the file with 2 spaces.
Just follow these steps below:
1.Select file,press F2.
2.Hold alt key and type 0160 from the numpad.
3.Release the alt key.
Now without doing anything else,again hold alt key and press 0160.
4.Press enter and you will have second nameless file in the same directory.
5.Repeat step 3 to create as many nameless files or folders in the same directory
This is one of the ultimate tricks.
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Evolution of Computers (Computer's History)
Early Start :
Computers have been around for quite a few years. Some of your parents were probably around in 1951 when the first computer was bought by a business firm. Computers have changed so rapidly many people can not keep up with changes.
One newspaper tried to relate how the fast changes in computer technology would look to a similar pace in the auto industry:
"Had the automobile developed at a pace (equal) to that of the computer during the past twenty years, today a Rolls Royce would cost less than $3.00, get 3 million miles to the gallon, deliver enough power to drive (the ship) the Queen Elizabeth II, and six of them would fit on the head of a pin!"
These changes have occurred so rapidly that many people do not know how our modern computer got its start.
The First Computing Machines "Computers"
Since ancient times, people have had ways to deal with data and numbers. Early people tied knots in rope and carved marks on clay tablets to keep track of livestock and trade. Some people considered the 5000 year old ABACUS-- a frame with beads strung on wires to be the first true computing aid.
As trade and tax system grew in complexity, people saw that faster, more reliable and exact tools were needed for doing math and keeping records.
In the mid-1600's, Blaise Pascal and his father, who was a tax officer himself, were working on taxes for the French government in Paris. The two spent hours figuring and refiguring taxes that each citizen owed. Young Blaise decided in 1642 to build an adding and subtraction machine that could aide in such a tedious and time consuming process. The machine Blaise made had a set of eight gears that worked together much like an odometer keeps track of a car's mileage. His machine encountered many of problems. For one, it was always breaking down. Second, the machine was slow and extremely costly. And third, people were afraid to use the machine thinking it might replace their jobs. Pascal later became famous for math and philosophy, but he is still remember for his role in computer technology. In his honor, there is a computer language named Pascal.
The next big step for computers arrived in the 1830's when Charles Babbage decided to build a machine to help him complete and print mathematical tables. Babbage was a mathematician who taught at Cambridge University in England. He began planning his calculating machine calling it the Analytical Engine. The idea for this machine was amazingly like the computer we know today. It was to read a program from punched cards, figure and store the answers to different problems, and print the answer on paper. Babbage died before he could complete the machine. However because of his remarkable ideas and work, Babbage is know as the Father of Computers.
The next huge step for computers came when Herman Hollerith entered a contest given by the U.S. Census Bureau. The contest was to see who could build a machine that would count and record information faster. Hollerith, a young man working for the Bureau built a machine called the Tabulating Machine that read and sorted data from punched cards. The holes punched in the cards matched each person's answers to questions. For example, married, single, and divorces were answers on the cards. The Tabulator read the punched cards as they passed over tiny brushes. Each time a brush found a hole, it completed an electrical circuit. This caused special counting dials to increase the data for that answer.
Thanks to Hollerith's machine, instead of taking seven and a half years to count the census information it only took three years, even with 13 million more people since the last census. Happy with his success, Hollerith formed the Tabulating Machine Company in 1896. The company later was sold in 1911. And in 1912 his company became the International Business Machines Corporation, better know today as IBM.
The First Electric Powered Computer
What is considered to be the first computer was made in 1944 by Harvard's Professor Howard Aiken. The Mark I computer was very much like the design of Charles Babbage's having mainly mechanical parts, but with some electronic parts. His machine was designed to be programmed to do many computer jobs. This all-purpose machine is what we now know as the PC or personal computer. The Mark I was the first computer financed by IBM and was about 50 feet long and 8 feet tall. It used mechanical switches to open and close its electric circuits. It contained over 500 miles of wire and 750,000 parts.
The First All Electronic Computer
The first all electronic computer was the ENIAC (Electronic Numerical Integrator and Computer). ENIAC was a general purpose digital computer built in 1946 by J. Presper Eckert and John Mauchly. The ENIAC contained over 18,000 vacuum tubes (used instead of the mechanical switches of the Mark I) and was 1000 times faster than the Mark I. In twenty seconds, ENIAC could do a math problem that would have taken 40 hours for one person to finish. The ENIAC was built the time of World War II had as its first job to calculate the feasibility of a design for the hydrogen bomb. The ENIAC was 100 feet long and 10 feet tall.
M ore Modern Computers
A more modern type computer began with John von Neumann's development of software written in binary code. It was von Neumann who began the practice of storing data and instructions in binary code and initiated the use of memory to store data, as well as programs. A computer called the EDVAC (Electronic Discrete Variable Computer) was built using binary code in 1950. Before the EDVAC, computers like the ENIAC could do only one task then they had to be rewired to perform a different task or program. The EDVAC's concept of storing different programs on punched cards instead of rewiring computers led to the computers that we know today.
While the modern computer is far better and faster than the EDVAC of its time, computers of today would not have been possible with the knowledge and work of many great inventors and pioneers.
Have you used a computer recently?
"Yes" may be the right answer for the question.
If you have made a phone call, ridden in a car, watched a TV, played a video game you have used a computer. Even as you read this paper, keep in mind the words you are reading were put into type by a computer.
Here is a list of statements about computers. Decide whether each statement is true or false .
Computers are smarter than humans.
Computers have brains.
Some computers have feelings.
Computers can solve any problems.
You need to know a lot of science and math to use a computer.
If you decided that each statement is false, you are correct. Then what is a computer? What can it do? It is a machine that can handle large amounts of information and work with amazing speed. A computer is built to do these four jobs:
Computers are conformed to follow instructions from humans. They can solve only the problems that people tell them to solve. Since people cannot solve every problem, neither can computers. To tell a computer what to do, you have to know what problem you want to solve and have a plan for solving it.
Since computers can't do anything without instructions from a human, what makes them so special? They can do some things better than humans. Computers calculate faster than humans. They are more accurate than humans. Computer can also store vast amounts of information, and they do not "forget" what they store. These kinds of qualities make computer wonderful tools to help people solve complex problems.
Computers have become important and valuable tools in today's world. Since they affect so many parts of our lives, it is important to be aware of how they are used and how they work.
~~ Roderick Hames