LOCAL BUSES(Exercise 2)

A computer bus is a method of transmitting data from one part of the computer to another part of the computer. The computer bus will connect all devices to the computer CPU and main memory. The computer bus consists of two parts, the address bus and a data bus. The data bus transfers actual data, whereas the address bus transfers information about where the data should go.
This page contains a basic overview of each of the computer buses as well as related links to each bus.
ISA
Introduced by IBM, ISA or Industry Standard Architecture was originally an 8-bit bus that was later expanded to a 16-bit bus in 1984. When this bus was originally released it was a proprietary bus, which allowed only IBM to create peripherals and the actual interface. However, in the early 1980's other manufacturers were creating the bus.
In 1993, Intel and Microsoft introduced a PnP ISA bus that allowed the computer to automatically detect and setup computer ISA peripherals, such as a modem or sound card. Using the PnP technology, an end-user would have the capability of connecting a device and not having to configure the device using jumpers or dipswitches.
To determine if an ISA card is an 8-bit or 16-bit card, physically look at the card. You will notice that the first portion of the slot closest to the back of the card is used if the card is an 8-bit card. However, if both sections of the card are being utilized, the card is a 16-bit card.
Many manufacturers are trying to eliminate the usage of the ISA slots; however, for backwards compatibility you may find 1 or 2 ISA slots with additional PCI slots, AGP slots, etc. However, today you may also have a motherboard that has no ISA slots. We highly recommend, when purchasing any new internal expansion card, that you stay away from ISA as it has, for the most part, disappeared.
MCA
Short for Micro Channel Architecture, MCA was introduced by IBM in 1987. MCA, or the Micro Channel bus, was a competition for ISA bus. The MCA bus offered several additional features over the ISA such as a 32-bit bus, automatically configure cards (similar to what Plug and Play is today), and bus mastering for greater efficiency.
One of the major downfalls of the MCA bus was it being a proprietary bus and because of competing bus designs. The MCA bus never became widely used and has since been fazed out of the desktop computers.
EISA
Short for Extended Industry Standard Architecture, EISA was announced September of 1988. EISA is a computer bus designed by 9 competitors to compete with IBM's MCA bus. These competitors were AST Research, Compaq, Epson, Hewlett Packard, NEC, Olivetti, Tandy, WYSE, and Zenith Data Systems.
The EISA bus provided 32-bit slots at an 8.33 MHz cycle rate for the use with 386DX or higher processors. In addition, the EISA can accommodate a 16-bit ISA card in the first row.
Unfortunately, while the EISA bus is backwards compatible and is not a proprietary bus, the EISA bus never became widely used and is no longer found in computers today.VLB
The VESA (Video Electronics Standards Association) is a nonprofit organization founded by NEC. The VLB, or VESA Local Bus, 1.0 was released in 1992. The VLB is a 32-bit bus that had direct access to the system memory at the speed of the processor, commonly the 486 CPU (33 / 40 MHz). VLB 2.0 was later released in 1994 and had a 64-bit bus and a bus speed of 50 MHz. Unfortunately, because the VLB heavily relied on the 486 processor, when the Pentium Processor arose in the Market place, manufacturers began switching to PCI.
PCI
Introduced by Intel in 1992, revised in 1993 to version 2.0, and later revised in 1995 to PCI 2.1. PCI is short for Peripheral Component Interconnect and is a 32-bit computer bus that is also available as a 64-bit bus today.
The PCI bus is the most commonly used and found bus in computers today.

PORTS
An interface port is a socket on the outside of the PC's case that allows you to connect external devices such as keyboards, mice, printers, scanners, digital cameras and joysticks. You can purchase circuit cards to add additional ports, but only if you have slots available and your motherboard supports this type of upgrade.
Keyboard/mouse portMany systems have ports for plugging in a keyboard and mouse or other device.
Serial portSerial ports can only accommodate one device at a time, and they're slow compared to USB ports.
Joystick/game portThese ports are now used for older joysticks and other gaming devices that aren't compatible with any of the newer interfaces.
USB 1.1Most PCs come with at least one USB port. USB ports are the most popular type of port, and allow for high-speed communication (up to 12Mbps) between external devices and your computer. Printers, scanners, digital cameras and many other peripherals use this port. USB-compatible devices may be connected to your PC through the USB port on the back of the computer or through a USB hub.
USB 2.0An upgrade of USB 1.1, USB 2.0 boasts a 480Mbps data transfer rate. USB 2.0, also called High-Speed USB, is compatible with CD and DVD drives, USB 2.0 features total backward compatibility with the older interface. The 2.0 interface requires a PCI adapter card for PCs, and a PCMIA card for notebook computers to allow for the massive amount of data transfer.
Shop for
• Accesories and Add-Ons
IEEE1394It goes by several different names; Sony, for example, calls it i.Link™, and Apple calls it FireWire®. IEEE1394 ports and cables are designed to transmit images and video in a purely digital format between your system and other devices, such as a digital camcorders and cameras. This interface runs slightly slower than USB 2.0 at 400Mbps, but is essential for anyone interested in digital imaging applications.

READ ONLY MEMORY
Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified (at least not very quickly or easily), it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to require frequent updates).
Modern semiconductor ROM chips are not immediately distinguishable from similar chips like RAM modules, except by the part numbers printed on the package.
In its strictest sense, ROM refers only to mask ROM (the oldest type of solid state ROM), which is fabricated with the desired data permanently stored in it, and thus can never be modified. However, more modern types such as EPROM and flash EEPROM can be erased and re-programmed multiple times; they are still described as "read-only memory" because the reprogramming process is generally infrequent, comparatively slow, and often does not permit random access writes to individual memory locations, which are possible when reading a ROM. Despite the simplicity of mask ROM, economies of scale and field-programmability often make reprogrammable technologies more flexible and inexpensive, so that mask ROM is rarely used in new products as of 2007.
Contents[show]
1 History
1.1 Use of ROM for program storage
1.2 ROM for data storage
2 Types of ROMs
2.1 Semiconductor based
2.2 Other technologies
2.2.1 Historical examples
3 Speed of ROMs
3.1 Reading speed
3.2 Writing speed
4 Endurance and data retention
5 ROM images
6 See also
7 References
8 External links
//

[edit] History
The simplest type of solid state ROM is as old as semiconductor technology itself: combinatorial logic gates can be joined manually to map n-bit address input onto arbitrary values of m-bit data output (a look-up table). With the invention of the integrated circuit came mask ROM. Mask ROM consists of a grid of word lines (the address input) and bit lines (the data output), selectively joined together with transistor switches, and can represent an arbitrary look-up table with a regular physical layout and predictable propagation delay.
In mask ROM, the data is physically encoded in the circuit, so it can only be programmed during fabrication. This leads to a number of serious disadvantages:
It is only economical to buy mask ROM in large quantities, since users must contract with a foundry to produce a custom design.
The turnaround time between completing the design for a mask ROM and receiving the finished product is long, for the same reason.
Mask ROM is impractical for R&D work since designers frequently need to modify the contents of memory as they refine a design.
If a product is shipped with faulty mask ROM, the only way to fix it is to recall the product and physically replace the ROM.
Subsequent developments have addressed these shortcomings. PROM, invented in 1956, allowed users to program its contents exactly once by physically altering its structure with the application of high-voltage pulses. This addresses problems 1 and 2 above, since a company can simply order a large batch of fresh PROM chips and program them with the desired contents at its designers' convenience. The 1971 invention of EPROM essentially solved problem 3, since EPROM (unlike PROM) can be repeatedly reset to its unprogrammed state by exposure to strong ultraviolet light. EEPROM, invented in 1983, went a long way to solving problem 4, since an EEPROM can be programmed in-place if the containing device provides a means to receive the program contents from an external source (e.g. a personal computer via a serial cable). Flash memory, invented at Toshiba in the mid-1980s, and commercialized in the early 1990s, is a form of EEPROM that makes very efficient use of chip area and can be erased and reprogrammed thousands of times without damage.
All of these technologies improved the flexibility of ROM, but at a significant cost-per-chip, so that in large quantities mask ROM would remain an economical choice for many years. (Decreasing cost of reprogrammable devices had almost eliminated the market for mask ROM by the year 2000.) Furthermore, despite the fact that newer technologies were increasingly less "read-only," most were envisioned only as replacements for the traditional use of mask ROM.
The most recent development is NAND flash, also invented by Toshiba. Its designers explicitly broke from past practice, stating plainly that "the aim of NAND Flash is to replace hard disks,"[1] rather than the traditional use of ROM as a form of non-volatile primary storage. As of 2007, NAND has partially achieved this goal by offering throughput comparable to hard disks, higher tolerance of physical shock, extreme miniaturization (in the form of USB flash drives and tiny microSD memory cards, for example), and much lower power consumption.

[edit] Use of ROM for program storage
Every stored-program computer requires some form of non-volatile storage to store the initial program that runs when the computer is powered on or otherwise begin execution (a process known as bootstrapping). Likewise, every non-trivial computer requires some form of mutable memory to record changes in its state as it executes.
Forms of read-only memory were employed as non-volatile storage for programs in most early stored-program computers, such as ENIAC after 1948 (until then it was not a stored-program computer as every problem had to be manually wired into the machine, which could take days to weeks). Read-only memory was simpler to implement since it required only a mechanism to read stored values, and not to change them in-place, and thus could be implemented with very crude electromechanical devices (see historical examples below). With the advent of integrated circuits in the 1960s, both ROM and its mutable counterpart static RAM were implemented as arrays of transistors in silicon chips; however, a ROM memory cell could be implemented using fewer transistors than an SRAM memory cell, since the latter requires a latch (comprising 5-20 transistors) to retain its contents, while a ROM cell might consist of a the absence (logical 0) or presence (logical 1) of a single transistor connecting a bit line to a word line.[2] Consequently, ROM could be implemented at a lower cost-per-bit than RAM for many years.
Many home computers of the 1980s stored a BASIC interpreter or operating system in ROM. ROM was more economical than RAM, and other forms of non-volatile storage such as magnetic disk drives were too expensive to be included with every home computer. For example, the celebrated Commodore 64 included 64 KiB of RAM and 20 KiB of ROM contained a BASIC interpreter and the "KERNAL" (sic) of its operating system. Later home or office computers such as the IBM PC XT often included magnetic disk drives, and larger amounts of RAM, allowing them to load their operating systems from disk into RAM, with only a minimal hardware initialization core and bootloader remaining in ROM (known as the BIOS in IBM-compatible computers). This arrangement allowed for a more complex and easily upgradeable operating system.
In modern general-purpose computers, there is little reason to store any program code or data in read-only memory: secondary storage devices such as hard disks are fast, ubiquitous, and rapidly decreasing in cost per bit, and large capacity dynamic RAM modules are cheaper than ROM thanks to economies of scale and more efficient designs. In modern PCs, ROM is used only to store basic bootstrapping firmware, such as the legacy BIOS which persists in most x86-based systems; even this limited "read-only" memory is likely to be implemented as Flash ROM (see below) to permit in-place reprogramming should the need for a firmware upgrade arise.
ROM and its successor technologies remain prevalent in embedded systems, such as MP3 players, set-top boxes, and broadband routers, all of which are designed to achieve more restricted functions than general-purpose computers, but which are nonetheless based on general-purpose microprocessors in most cases. These devices often store all of their program code in ROM since they usually lack mass storage peripherals (e.g. hard disks) for reasons of cost, portability, and power consumption. Furthermore, since the software is usually tightly coupled to the hardware, changes to the software are rarely needed. Nonetheless, as of 2007 nearly all of these devices use Flash rather than mask ROM, and many provide some means to connect the device to a personal computer for firmware updates (for example, a digital audio player's firmware might be updated to support a new music file format). Hobbyists have taken advantage of this flexibility to reprogram such devices to new purposes; for example, the iPodLinux and OpenWRT projects have enabled users to run full-featured Linux distributions on their MP3 players and wireless routers, respectively.
It is also useful for binary storage of cryptographic data, as it makes them difficult to replacement, which may be desirable in order to enhance information security.

[edit] ROM for data storage
Since ROM (at least in hard-wired mask form) cannot be modified, it is really only suitable for storing data which is not expected to need modification for the life of the device. To that end, ROM has been used in many computers to store look-up tables for the evaluation of mathematical and logical functions (for example, a floating-point unit might tabulate the sine function in order to facilitate faster computation). This was especially effective when CPUs were slow and ROM was cheap compared to RAM.
Notably, the display adapters of early personal computers stored tables of bitmapped font characters in ROM. This usually meant that the text display font could not be changed interactively. This was the case for both the CGA and MDA adapters available with the IBM PC XT.
The use of ROM to store such small amounts of data has disappeared almost completely in modern general-purpose computers. However, Flash ROM has taken over a new role as a medium for mass storage or secondary storage of files and programs, comparable to hard disks. This usage enabled by the development of NAND flash, which features high endurance, efficient use of chip area (and thus low cost-per-bit), and high read/write throughput. Although NAND flash developed from earlier ROM-like technologies, its current use bears little resemblance to the original function of ROM.

[edit] Types of ROMs

The first EPROM, an Intel 1702, with the die and wire bonds clearly visible through the erase window.

[edit] Semiconductor based
Classic mask-programmed ROM chips are integrated circuits that physically encode the data to be stored, and thus it is impossible to change their contents after fabrication. Other types of non-volatile solid-state memory permit some degree of modification:
Programmable read-only memory (PROM), or one-time programmable ROM (OTP), can be written to or programmed via a special device called a PROM programmer. Typically, this device uses high voltages to permanently destroy or create internal links (fuses or antifuses) within the chip. Consequently, a PROM can only be programmed once.
Erasable programmable read-only memory (EPROM) can be erased by exposure to strong ultraviolet light (typically for 10 minutes or longer), then rewritten with a process that again requires application of higher than usual voltage. Repeated exposure to UV light will eventually wear out an EPROM, but the endurance of most EPROM chips exceeds 1000 cycles of erasing and reprogramming. EPROM chip packages can often be identified by the prominent circular "window" which allows UV light to enter. After programming, the window is typically covered with a label to prevent accidental erasure. Some EPROM chips are factory-programmed before they are packaged, and include no window; these are effectively PROM.
Electrically erasable programmable read-only memory (EEPROM) is based on a similar semiconductor structure to EPROM, but allows its entire contents (or selected banks) to be electrically erased, then rewritten electrically, so that they need not be removed from the computer (or camera, MP3 player, etc.). Writing or flashing an EEPROM is much slower (milliseconds per bit) than reading to a ROM or writing to a RAM (nanoseconds in both cases).
Electrically alterable read-only memory (EAROM) is a type of EEPROM that can be modified one bit at a time. Writing is a very slow process and again requires higher voltage (usually around 12 V) than is used for read access. EAROMs are intended for applications that require infrequent and only partial rewriting. EAROM may be used as non-volatile storage for critical system setup information; in many applications, EAROM has been supplanted by CMOS RAM supplied by mains power and backed-up with a lithium battery.
Flash memory (or simply flash) is a modern type of EEPROM invented in 1984. Flash memory can be erased and rewritten faster than ordinary EEPROM, and newer designs feature very high endurance (exceeding 1,000,000 cycles). Modern NAND flash makes efficient use of silicon chip area, resulting in individual ICs with a capacity as high as 16 GB as of 2007; this feature, along with its endurance and physical durability, has allowed NAND flash to replace magnetic in some applications (such as USB flash drives). Flash memory is sometimes called flash ROM or flash EEPROM when used as a replacement for older ROM types, but not in applications that take advantage of its ability to be modified quickly and frequently.
By applying write protection, some types of reprogrammable ROMs may temporarily become read-only memory.

[edit] Other technologies
There are other types of non-volatile memory which are not based on solid-state IC technology, including:
Optical storage media, such CD-ROM which is read-only (analogous to masked ROM). CD-R is Write Once Read Many (analogous to PROM), while CD-RW supports erase-rewrite cycles (analogous to EEPROM); both are designed for backwards-compatibility with CD-ROM.

[edit] Historical examples

Transformer matrix ROM (TROS), from the IBM System 360/20
Diode matrix ROM, used in small amounts in many computers in the 1960s as well as electronic desk calculators and keyboard encoders for terminals. This ROM was programmed by installing discrete semiconductor diodes at selected locations between a matrix of word line traces and bit line traces on a printed circuit board.
Resistor, capacitor, or transformer matrix ROM, used in many computers until the 1970s. Like diode matrix ROM, it was programmed by placing components at selected locations between a matrix of word lines and bit lines. ENIAC's Function Tables were resistor matrix ROM, programmed by manually setting rotary switches. Various models of the IBM System/360 and complex peripherial devices stored their microcode in either capacitor (called BCROS for Balanced Capacitor Read Only Storage on the 360/50 & 360/65 or CCROS for Card Capacitor Read Only Storage on the 360/30) or transformer (called TROS for Transformer Read Only Storage on the 360/40 and others) matrix ROM.
Core rope, a form of transformer matrix ROM technology used where size and/or weight were critical. This was used in NASA/MIT's Apollo Spacecraft Computers, DEC's PDP-8 computers, and other places. This type of ROM was programmed by hand by weaving "word line wires" inside or outside of ferrite transformer cores.
The perforated metal character mask ("stencil") in Charactron cathode ray tubes, which was used as ROM to shape a wide electron beam to form a selected character shape on the screen either for display or a scanned electron beam to form a selected character shape as an overlay on a video signal.
Various mechanical devices used in early computing equipment. A machined metal plate served as ROM in the dot matrix printers on the IBM 026 and IBM 029 key punches.

[edit] Speed of ROMs

[edit] Reading speed
Although the relative speed of RAM vs. ROM has varied over time, as of 2007 large RAM chips can be read faster than most ROMs. Therefore, ROM content is sometimes copied to RAM or shadowed before its first use, and subsequently read from RAM.

[edit] Writing speed
For those types of ROM that can be electrically modified, writing speed is always much slower than reading speed, and it may require unusually high voltage, the movement of jumper plugs to apply write-enable signals, and special lock/unlock command codes. Modern NAND Flash achieves the highest write speeds of any rewritable ROM technology, with speeds as high as 15 MiB/s (or 70 ns/bit), by allowing (indeed requiring) large blocks of memory cells to be written simultaneously.

[edit] Endurance and data retention
Because they are written by forcing electrons through a layer of electrical insulation onto a floating transistor gate, rewriteable ROMs can withstand only a limited number of write and erase cycles before the insulation is permanently damaged. In the earliest EAROMs, this might occur after as few as 1,000 write cycles, while in modern Flash EEPROM the endurance may exceed 1,000,000, but it is by no means infinite. This limited endurance, as well as the higher cost per bit, means that Flash-based storage is unlikely to completely supplant magnetic disk drives in the near future.
The timespan over which a ROM remains accurately readable is not limited by write cycling. The data retention of EPROM, EAROM, EEPROM, and Flash may be limited by charge leaking from the floating gates of the memory cell transistors. Leakage is exacerbated at high temperatures or in high-radiation environments. Masked ROM and fuse/antifuse PROM do not suffer from this effect, as their data retention depends on physical rather than electrical permanence of the integrated circuit (although fuse re-growth was once a problem in early fused PROMs).

[edit] ROM images

EXERCISE 2

Personal Computer Buses
This is a subdivision of the main Interface Bus Tree for PC buses. This page provides descriptions for common PC expansion buses and peripheral buses. Interface Buses designed to operate with Personal Computers [PC's] are listed below. Some of these bus types may also operate over a back plane and or a cable. Each listing below has a brief description, use the link if provided for a more detailed description of the bus and to access links to component and IC manufacturers, connector pin outs, signal names, or specifications. The buses are used on IBM PC or Apple computers. A few SUN buses are also provided. Video buses operating over a cable between the computer and the monitor are listed all together near the bottom of the page, or may be found on a separate page, PC Video Monitor Buses. A table which compares many of the more common Personal Computer bus types is provided at the bottom of the page.
PC Cable & Slot Buses
AC97 {Audio Codec '97 interface specification defines audio and Modem functionality for PC systems. The AC97 standard is not really a bus. AC97 was developed by intel in 1997.}
Access Bus {Is a low speed serial bus aimed at the PC market for connecting peripheral devices. Access Bus is also used in the Display Data Channel [DDC] video standard for bi-directional communication between the video monitor and PC. Access.Bus uses the I2C bus as the electrical hardware interface. AccessBus uses a serial clock and serial data line operating at 100Kbps over a 10-meter cable}
ACR Bus {Advanced Communication Riser, another Computer OEM Riser specification. This latest version provides for modem support, LAN and xDSL support, and Audio support. ACR was preceded by CNR and AMR, both listed on this page. The ACR standard is backwards compatible with AMR. Additional description of Riser cards is also listed below.}
ADB Bus {Apple Desktop Bus was a serial bus used by Apple computer to drive the mouse and keyboard. The cable consisted of one data line [ADB], a power line [+5v] and a ground line. The maximum data rate was 125kbps. The ADB bus is OBSOLETE, replaced by the Firewire bus.}
AGP Bus {The Accelerated Graphics Port [AGP], is used as a Video Local bus on the Personal Computer. The AGP bus was derived from the Parallel PCI bus with a few additional signals. The AGP Bandwidth is 2.1GB/s. The PCI-Express card bus has replaced the AGP bus on personal computers.}
AIMM Bus {AGP Inline Memory Module [AIMM] defines a memory card that plugs into the AGP slot, on motherboards with an integrated graphics core [that don't require a Video card]. The AIMM card provides an additional 4MB of dedicated video memory. This interface solution is OBSOLETE.}
AMR Bus {Audio/Modem Riser specification defines a hardware scalable OEM PC mother board riser board and interface, which supports both audio and modem functions. An MR slot will provide a Modem function, while an AMR slot will provide both an Audio and Modem function. The modem is a WinModem. }
Apple Computer Buses {Apple and Macintosh [MAC] Computer Buses, pinout tables.}
AT Bus {ISA AT Computer Card Bus description. The PC-AT bus was replaced by the PCI bus. PCAT is OBSOLETE.}
ATA Bus {IDE/ATA Personal Computer [PC] Parallel Bus used as an interconnect between Mother boards and Hard drives, Disk drives, Floppy or CD drives. IDE: Integrated Drive Electronics, ATA: Advanced Technology Attachment. There is no difference between the IDE and ATA interface buses. The maximum bus speed is 133MBps, with a maximum ribbon cable of 18 inches.}
ATX Form Card Connector Pinout {The ATX Form Card was designed to up-grade the old AT form factor mother board to allow for ATX connectors. This turned out into translating a dual-pin header located on the AT motherboard into a connector on the rear I/O panel. This predates the defined I/O connectors on the ATX motherboard form-factor. The page provides the pinout for the ATX Form Card interface.}
ATX Mother Board Connectors {Different types of header connector pinouts for the PC ATX Mother Board standard}
ATX Riser Card {Riser card used with ATX form factor mother boards. The ATX Riser card allows compact PC chassis designs with out expansion slots, additional slots are added in the vertical direction by using the Riser card which contains the slot connectors~ A compact PC chassis may be used with an ATX Mother Board, or a larger chassis can be designed using the same Mother Board and a Riser card, providing expansion slots.}
Audio Codec 97 {AC97 interface specification defines audio and Modem functionality for PC systems. The latest version of the specification was released in 2002 as revision 2.3 of the spec.}
CardBay {Places the USB onto the PC Card PCMCIA format. CardBay was released in 2001, not sure it if ever caught on, but has been obsoleted by the ExpressCard release. Refer to the PC Card listing, version 8.0 combined the USB interface.}
CardBus {was a 32 bit, 33MHz PCMCIA Card. CardBus replaced the 16 bit PC Card version of the PCMCIA standard}
C-Bus {and C-Bus II were developed by Corollary Inc. as a multiprocessing chip set architecture used with motherboards with more then one linked processor [4-way and 8-way systems]. Corollary Inc. was purchased by Intel in 1997. This bus may no longer being implemented.}
Centronics Parallel Port {Pin Outs for the Personal Computer [PC] Bi-Directional Parallel Peripheral Interface, mainly used as a Printer Bus. The Centronics bus had a maximum cable limit of around 12 feet. Refer to the IEEE-1248 page which replaced the Centronics bus. The Centronics bus is OBSOLETE, replaced by IEEE-1248.}
CMR Bus {(Chaintech Mulmedia Riser) used on Chaintech Mother Boards as a Chaintech Multimedia Card expansion slot, based on CMC7.1. This may be their implementation of the CNR specification.}
CNR Bus {The Communication and Networking Riser Specification defines a hardware scalable Original Equipment Manufacturer (OEM) mother board riser and interface that supports the audio, modem, and local area network (LAN) interfaces of core logic chipsets. This standard does not support an expansion slot, but an OEM built in board to include the Motherboard connector [CNR Connector]. Supported interface buses include, AC '97, SMBus and USB including Power and a LAN interface. The board size and pinouts are also defined in the specification. Intel no longer produces CNR slots on its Pentium 4 Processor Motherboards.}
CompactFlash Card {Mass Storage removable Flash Memory card operates like an ATA drive using Flash memory. Devices are about 1/3 the size of a Type II PC Card}
DataFlash Card {Mass Storage removable Flash Memory card. One of a number of removable Flash Memory cards.}
Device Bay {A defined form factor peripheral which connects via USB and/or Firewire to the PC, but as of 2001 is not supported by Windows. The specification may be obtained from the 1394 Trade Association}
DIB {Dual Independent Bus architecture was developed by intel. The DIB consists of 2 buses, the processor to main memory interface [Front-Side Bus], and the L2 cache bus [Back-Side Bus]. The DIB interface allowed the processor to simultaneously access L2 cache and system memory or I/O. The DIB architecture was also used with AMD processors}
DVI Bus {The DVI [Digital Visual Interface] is a standard for high-speed, high-resolution digital displays}
EIA-232 Bus {EIA232 is the standard Serial Port interface [bus] used with personal computers. The maximum speed is rated at 20kbps, over a maximum cable distance of 20 meters. EIA-232 is the same standard as RS-232}
EISA {Extended Industry Standard Architecture [EISA] or Enhanced ISA bus: 8MHz @ 8/16/32 bits data bus, 32 bit address bus; PC Expansion Bus, compatible with ISA. An ISA card will work in an EISA slot, but an EISA card will not work in an AT slot. The EISA bus (in one mode) used both edges of the clock, with the rising edge used to output address, and the falling edge to place the data on the bus. Three other transfer modes were available. The EISA bus does not allow the board skirts common with the older XT cards. The EISA cards are the same physical size as the AT cards. The new address lines are termed "LA#", all address lines are latched. This bus is OBSOLETE and was replaced by the PCI and AGP buses. This page provides additional data on pin-out, signal names and board sizes; EISA PinOut}
Embedded PCI-X Specification {[ePCI-X], The PICMG 1.2 specification defines the mechanical and electrical interface to support a standard form factor PCI computer system with either two PCI/PCI-X busses or a single PCI/PCI-X bus. The document also defines the electrical and mechanical connections for a single board computer and backplane. This is an upgrade to the PCI-ISA specification. PCI-X capabilities are added to the PCI bus and the ISA bus is replaced by a second PCI-X bus, on the PCI-ISA backplane. The board retains the same mechanical dimensions as PCI-ISA but the components move to the PCI side and the slot occupies a PCI position on a backplane. Also refer to the PCI-ISA listing, or the PCI listing}
ePCI-X {Defined in the Embedded PCI-X listing.}
Ethernet Bus {The Ethernet Bus Standard is used as a Local Area Network [LAN]. The normal implementation is over a coax or twisted pair cable at either 10Mbps or 100Mbps}
Expansion_Buses for the Personal Computer.
ExpressCard {PCMCIA ExpressCard "Newcard" is the new form factor for PCMCIA Circuit Cards and will utilize either USB and PCI Express buses. The new single width card is 34mm x 75mm. The double width card is 54mm x 74mm (has a 22mm notch). The single card is called ExpressCard/34, and the double width card is called ExpressCard/54. Both cards are 5mm high.}
Fiber Channel {Used for transferring data to workstations, mainframes, supercomputers, desktop computers, storage devices, displays and peripherals [high-end server SANs]. Fibre Channel operates over fiber [400MBps] or copper [100MBps] cables}
FireWire Bus {The IEEE 1394 [FireWire] Bus, used as a high-speed serial bus between a PC and peripheral device}
Flash Memory Card buses There are a number of Flash memory card formats listed on this page, under their common standard or specification name. Flash Memory Card types include: SD Card, CompactFlash, SmartMedia...
Floppy Drive Bus {Pin Out Table}
Gigabit Ethernet {operates using either Shielded Twisted Pair [STP] copper, Un-Shielded Twisted Pair [UTP], or CAT-5 copper or fiber cable. Gigabit Ethernet also runs over a backplane at over 1GHz.}
GPA Bus {Graphics Performance Accelerator [GPA] defines a memory card that plugs into the AGP slot on mother boards with an integrated graphics core [don't require a Video card]. The AIMM card provides an additional 4MB of dedicated video memory. The previous name for this interface was AGP Inline Memory Module [AIMM]}
HD Audio {The new PC audio codec standard replacing AC97}
Hard-Drive buses {[before ATA or IDE] used to interface with hard drives include: XTA, ST506, and ESDI. XTA [XT Attachment] - Is a rarely used implementation of the ATA Interface that used an integrated 8 bit XT controller. ESDI [Enhanced Small Device Interface], was considered a successor to ST506/412 with faster transfer rates and supporting larger drive sizes. The ESDI bus used the same two-cable connection as the ST506. These interfaces are OBSOLETE and replaced by the ATA (IDE) bus.}
HTX Slot {Also called the HT slot for EATX server motherboards using HyperTransport Daughtercards}
HyperTransport Bus (A Point-to-Point bus with [at least] two unidirectional links; Uses 2, 4, 8, 16 or 32 bits [in each direction] with a data rate of 800Mbs/per pair with a 400MHz clock. Formally known as Lightning Data Transport (LDT). Used in mobile personal computers, servers, network equipment, embedded applications, and communications equipment)
IDE Bus {IDE/ATA Personal Computer [Parallel] Bus used for Hard drives, Floppy and CD drives. The Integrated Drive Electronics [IDE] bus, which is a 16-bit parallel interface, is being replaced by the Serial ATA bus [SATA]. The last version of the IDE bus [ATA-7] runs at 133MBps over an 18 inch ribbon cable.}
ISA/AT Bus {IBM Compatible ISA AT bus: 8MHz @ 8 and 16 bits data bus, 24 bit address bus, +/- 12 volts, +/- 5 volts, 15 Interrupt lines. The standard drive level is 24mA for all non-Open Collector signals on the bus. The AT card used the standard (edge) connector provided by the XT bus and added an additional (edge) connector behind that with the same pin-spacing @ 0.1 inch center-to-center. The additional connector has only 38 (19 per side) fingers, while the XT connector had 62 (32 per side) fingers. The Mother Board could then accept either an 8 or 16 bit card in an 8 bit slot (XT), or (if the connector was provided) a 16 bit card in an AT slot. The additional connector provided 4 additional address lines, and 8 additional data lines. The ISA AT bus is OBSOLETE, replaced by the PCI bus.}
ISA/XT Bus {IBM Compatible ISA XT bus: Obsolete; 4.77MHz @ 8 bits, +/- 12 volts, +/- 5 volts. The XT bus used a 62 pin (.1" center) edge connector; 31 pins per card side. Used a single oscillator of 14.31818MHz which was divided by 3. 8 Data lines, 0 to 7 (LSB=0). 20 Address lines, 0 to 19 (LSB=0). 1 Clock line (4.77MHz). 1 Reset line, 8 Interrupt lines. Some 8 bit cards have skirts which extend the board below the depth of the top of the connector to allow additional circuitry. These cards, with skirts, are not compatible with the 16 bit AT bus. The XT bus uses connector J1 (A/B), AT uses J1 (A/B), J2 (C/D). The ISA XT bus is OBSOLETE, replaced by the ISA AT bus.} This page lists the PC XT Bus pinout
IEEE-1284 {Personal Computer [PC] Bi-Directional Parallel Peripheral Interface, mainly used as a Printer Bus, and a general purpose Parallel Peripheral Interface.}
iLink { is Sony's name for FireWire, i.Link is based on IEEE-1394 using conventional metallic conductors.}
JBus {developed by Sun for its computers, is a 128 bits wide bus, at 200MHz [with three loads], and features 16 to 64 Gbytes/s on-chip. However, JBus delivers only 3.2 Gbytes/s when used as an off-chip bus.. JBus uses 170-pins on a 300-pin connector. JBus uses 1.5volt DTL [Dynamic Termination Logic] devices.}
Joystick Interface Bus { The Joystick port used with Personal Computers uses a 15pin D connector and has the following pin out: Pin 1; +5Vdc, Pin 2; Joystick/A Right Button, Pin 3; Joystick/A X-Coordinate, Pin 4; Ground, Pin 5; Ground, Pin 6; Joystick/A Y-Coordinate, Pin 7; Joystick/A Left Button, Pin 8; +5Vdc, Pin 9; +5V dc, Pin 10; Joystick/B Right Button, Pin 11; Joystick/B X-Coordinate, Pin 12; MIDI Out, Pin 13; Joystick/B Y-Coordinate, Pin 14; Joystick/B Left Button, Pin 15; MIDI In}
Keyboard Interface Bus {The serial Keyboard used on Personal Computers [PCs] is a [PS/2] 6 pin Circular DIN. The pin-out for the Keyboard or Mouse port is: Pin 1; Data, Pin 2; Reserved, Pin 3; Ground, Pin 4; +5 Vdc, Pin 5; Clock, Pin 6; Reserved. Another variant may be seen as a 5-pin DIN; using Pin 1; Clock, Pin 2; Data, Pin 3; Reserved, Pin 4; Ground, Pin 5; +5 volts. Some newer computers may have USB ports [listed below] to handle this function}
LPT {port, [line printer terminal] an old term which now refers to a parallel port interface. The two main parallel port interfaces include the Centronics interface or the IEEE 1284 interface. Both interfaces are listed on this page. The parallel port is slowing it's age and in some cases may be replaced by an USB interface or Ethernet port.}
Macintosh Computer Buses {Apple and Macintosh [MAC] Computer Buses; Connector Pin-Outs only}
MCA {Micro Channel Architecture bus: Designed to correct the problems with the ISA bus, but never caught on out side of IBM machines. The bus is Obsolete and was later replaced by the PCI bus.; 10MHz @ 16 or 32 bits, uP independent, asynchronous, IBM proprietary on PS2 computers. With bus enhancements the speed reaches 80MBps, using clock doubling.}
Memory Stick Flash {Memory Stick Flash is another flash memory card format type. The device size is 50 mm x 21 mm x 2.8 mm}
MIDI Interface Bus {[Musical Instrument Digital Interface] uses a 5-pin circular DIN connector. There are three different pinouts for; MIDI In, MIDI Out, and MIDI Thru. The MIDI signals are also found on the on a standard sound card Joystick/MIDI 15-pin connector. MPU401: [MIDI Processing Unit 401], Developed by Roland. }
Mini PCI {Is a small form factor version of a PCI card. Mini PCI uses a subset of the PCI specification, and is electrically identical to the Peripheral Component Interface. Mini PCI uses a 32 bit data bus running at 3.3v. The board uses 124-pin fingers. There are Type I and Type II, and Type III daughter-boards. Dimensions [General] for a Type IIIA are 59.75 mm x 50.95 mm x 5mm. Mini PCI was designed for the NoteBook/ Laptop market, i.e mobile systems.}
Mini PCI Express {Is a small form factor version of a PCI Express card. Mini PCI Express was designed for the NoteBook/ Laptop market, i.e mobile systems. The board size is 51mm x 30mm. More Mini PCI EXpress cards can fit within a Lap-top because they are about half the size of a Mini PCI board.}
Miniature Card {Miniature Card is a smaller implementation of PCMCIA. Miniature Cards dimensions: 3.5mm x 33mm x 38mm (TxLxW). The electrical specifications are a subset of the PC Card standard, restricted to memory applications only. It uses a 16-bit data bus and a 24-bit address bus to allow a single card to store up to 64MB.}
Mouse Interface Bus {The serial mouse used on Personal Computers [PCs] is a 6 pin Circular DIN. The pin-out for the Keyboard or Mouse port is: Pin 1; Data, Pin 2; Reserved, Pin 3; Ground, Pin 4; +5 Vdc, Pin 5; Clock, Pin 6; Reserved. As of mid 2005 some computers are shipping without this interface, favoring a USB connection instead.}
Modem Interface Bus {A listing of International Telegraphic Union Modem standards}
Mother Board Types {A listing of different Mother Board types and their sizes; ATX and EBX for example, many others listed}
Multimedia Card {Multimedia Card [MMC] is another flash memory card format type. The device size is 32 mm x 24 mm x 1.4 mm}
NUbus {IEEE Std 1196-1987 Simple 32-Bit Backplane Bus; NuBus. An Apple [Macintosh and NeXT Computer] expansion bus with 32 bit address and 32 bit data bus operating at 10MHz, with a throughput of 40MBps. The card had a form factor of 12" x 7", and used a standard 96-pin three-row (VME) connector. NuBus90, increased the clock rate to 20Mhz providing a throughput of 70Mbps. Nubus is OBSOLETE, replaced by the PCI bus.}
OP iLink {Sony's name for FireWire; OP i.Link is based on IEEE1394a-2000 using single-core plastic optical fiber.}
PATA Disk Drive Bus {The un-official name for IDE/ATA Personal Computer [Parallel] Bus used for Hard disk drives, Floppy and CD drives. The Integrated Drive Electronics [IDE] bus is a 16-bit parallel cable interface, replaced by the Serial ATA bus [SATA]. The last version of the IDE bus [ATA-7] runs at 133MBps over an 18 inch ribbon cable.}
PC Bus {XT, AT, ISA, and EISA Computer Card Bus descriptions, all were replaced by the PCI bus. These buses are OBSOLETE.}
PC/104 Bus {PC/104 Bus is used as an embedded PC bus, combining the IBM compatible ISA buses; XT, and AT buses into a different form factor [Card size]. The boards stack on top of each other. PCI/104-Plus introduces the PCI bus, and PCI/104 removes the IBM PC XT and AT buses leaving only the PCI in an embedded form factor. The IBM 4MHz XT bus width of 8 bits, along with the 16 bit AT bus is used in another card size. The PCI/104-Plus specification added the 33MHz PCI bus. The PCI-104 standard also relates to the 33MHz PCI bus, but removes the ISA buses. The standard does not support 66MHz PCI.}
PCI Bus {The Peripheral Component Interface 'PCI' [Parallel] Bus was originally developed as a local bus expansion for the PC. The first version of the PCI bus ran at 33MHz with a 32 bit bus (133MBps), the current version runs at 66MHz with a 64 bit bus. The PCI bus operates either synchronously or asynchronously with the "mother Board bus rate: The page contains the PCI connector Pin-Outs}
PCI-X Bus {The Peripheral Component Interface [PCI-X] addendum is an enhancement to the current 64 bit 66MHz PCI bus specification. The minimum clock speed for PCI-X is 66MHz [PCI-X 66]. Additional bus speeds include: PCI-X 133, PCI-X 266 and PCI-X 533 providing up to 4.3GBps [PCI-X 1066 in the works]. PCI-X is backwards compatible with PCI. I believe the X stands for extension}
PCI Express Bus {Serial PCI Bus uses two low-voltage differential LVDS pairs, at 2.5Gb/s in each direction. Using 8B/10B encoding, and Supporting 1x, 2x, 4x, 8x, 12x, 16x, 32x bus widths. Set to replace the Parallel PCI bus; PCI, and PCI-X. PCIe is currently replacing the AGP slot on PC Mother Boards.}
PCI-ISA {A passive backplane which moves all active devices off the motherboard and onto a single card. The controller card used in the system has fingers [edge connectors] for both PCI and the ISA bus, the Mother Board only connectors. This allows additional cards to be added to the mother board which use either the ISA or PCI buses. Because only connectors reside on the mother board, repair time is increased, and down time is decreased. The standard is PICMG 1.0. The specification is used in embedded or industrial computer systems. A similar standard is PISA listed below. A newer standard called ePCI-X removes the obsolete ISA bus and replaces it with PCI-X interfaces.}
PCMCIA PC Card {Implementation of the 16 bit ISA Bus on a PCMCIA card: which is used as a removable card to supply storage or other functions to a PC. See Cardbus as an up-grade option.}
PCMCIA Cardbus {Implementation the 32 bit PCI bus in a PCMCIA form factor: which is used as a removable card to supply storage or other functions to a PC}
PCMCIA Miniature Card {Miniature Card is a smaller implementation of PCMCIA. Miniature Cards dimensions: 3.5mm x 33mm x 38mm (TxLxW). The electrical specifications are a subset of the PC Card standard, restricted to memory applications only. It uses a 16-bit data bus and a 24-bit address bus to allow a single card to store up to 64MB.}
PCMCIA ExpressCard {ExpressCard "Newcard" is the new form factor for PCMCIA Circuit Cards and will utilize either USB and PCI Express buses. The new single width card is 34mm x 75mm. The double width card is 54mm x 74mm (has a 22mm notch). The single card is called ExpressCard/34, and the double width card is called ExpressCard/54. Both cards are 5mm high.}
PictBridge {provides print services between devices like printers and digital cameras. The PictBridge standard is CIPA DC-001 and uses USB as the physical layer.}
PISA Bus {PC Expansion Bus [PCI + ISA]: A normal ISA card with an additional row of pins above the ISA pins. The new row of pins are used for the PCI bus. This card is normally only found in OEM industrial or embedded computers. the PISA standard was developed by Kontron. PISA is a combination ISA, and PCI bus in a short card form factor. In PISA's case the ISA and PCI fingers are on top of each other (but offset). You need a back plane designed to accept PISA cards, to use the PISA card. The PISA bus is used as an Industrial Embedded Computer Bus, not a consumer Personal Computer bus. A similar bus standard from PICMG uses both ISA and PCI interfaces but the pins [fingers] reside one after the other, not over top each other. PICMG 1.0 defines the PCI-ISA Card Edge Connector for Single Board Computers. A newer standard called ePCI-X removes the obsolete ISA bus and replaces it with PCI-X interfaces ~ PICMG 1.2.}
PISA express Bus {PC Expansion Bus [PCI + PCie]: modeled after the PISA Form Factor. The bus supports a maximum of two PCIe x1 slots, one PCIe x4 slot, one PCIe x16 slot, three PCI slots, one LPC bus, and two Express cards, the company says. Additionally, the standard includes power connections compatible with ATX and BTX motherboard standards. This card is normally only found in OEM industrial or embedded computers. Developed by Kontron}
QuickRing Bus {QuickRing, is an offshoot of SCI. QuickRing uses six data signals and a clock speed of 175 MHz to achieve a throughput of 200 MBytes/second/link. The six data signals use the SCI P1596.3 Low Voltage Differential Signaling (LVDS) protocol for low power dissipation and low noise immunity. The QuickRing Bus is OBSOLETE, replaced by the PCI bus}
RapidIO {RapidIO is used in High-performance embedded applications such as networking, storage, multimedia, and signal processing. RapidIO uses LVDS}
Reduced Size Multimedia Card {Reduced Size Multimedia Card [RS-MMC] is another flash memory card format type, the smaller version of MMC. The device size is 24 mm x 16 mm x 1.4 mm}
Riser Cards {Personal Computer Expansion Bus Riser Board standards include: ACR [Advanced Communication Riser], AMR [Audio/Modem Riser], and CMR [Communication and Networking Riser]. Each Riser standard has a listing on this page which may provide additional technical information about the standard. The Riser approach is designed to bring the basic wiring and control of a function to a riser slot [and board] so the function may be implemented with minimal cost off the Mother Board ~ with out the need for a PCI interface, for example. Computer OEM's [Original Equipment Manufacturers] would use a Riser slot [and board] to deliver a modem function at minimal cost.}
Riser Board {There is a secondary definition of Riser Card. In this case a Riser card is an 'extender' board which plugs into an expansion card slot. The extender rises up out of the slot to expose one or more identical bus slots (PCI-Express for example). These new slot connectors accept cards in the Horizontal direction. So a Mother Board which would have taken an expansion card in the vertical direction now because of the Riser Board allows cards to be Horizontal to the Mother Board. The link to Riser Boards points to OEM [Original Equipment Manufacturers] Card Manufacturers. This type of Riser Board is also listed on this page as an ATX Riser Board}
RS-232 Bus {RS232 is the standard Serial Port interface [bus] used with personal computers. The maximum speed is rated at 20kbps, over a maximum cable distance of 20 meters.}
S-100 Bus {Obsolete interface bus.}
SATA Bus {Serial ATA is the new four-wire Mother Board to Hard Disk Drive serial data bus, replacing the IDE [Parallel ATA] bus standard. Serial ATA uses only 4 signal pins, improving pin efficiency over the IDE interface which uses 26 signal pins going between devices [over an 80 conductor ribbon cable onto a 40 pin header connector]. The 4 lines are used for transmitting and receiving differential pairs, plus an additional three grounds pins and a separate power pin.}
Sbus {[IEEE-1496] is a computer expansion card bus used for Sun workstations. Sbus used a 32 bit address and data bus which run at 25MHz for data transfers of 100Mbps. Later increased to two 32 bit word transfers for a through-put of 200Mbps. Sbus is OBSOLETE, I think, replaced by the PCI bus. Note: Sun computer buses seem to mimic PC buses at this point.}
SCI Bus {Scalable Coherent Interface}; IEEE Std 1596-1992, SCI is a scalable network, nodes are interconnected in a point-to-point unidirectional link [ring]. The bandwidth grows with the number [concurrent] nodes used. SCI links are operate at 1 Gbps [serial], or 1 GBps [16-bit parallel], using a 250-MHz bi-phase clock over fiber optic or twisted-pair wires. Physical SCI controllers use LVDS signaling levels for 16 and 8 bit wide links.}
SCSI Bus {Small Computer Systems Interface [SCSI] is used as a 8 or 16-bit parallel interface used to attach peripheral devices to the PC. The latest version runs at 320MBps. SCSI was always much more expensive then IDE buses; how ever parallel SCSI is being replaced by Serial SCSI, listed below.}
SD Card {[Secure Digital] Card. A stamp-sized flash memory card which is removable. The Dimensions are 32 mm [height] x 24 mm [width] x 2.1 mm [thick] for an SD Card. While the miniSD Card is only 21.5 mm [height] x 20 mm [width] x 1.4 mm [thick]}
SDIO Card {[Secure Digital I/O] Card. A stamp-sized flash memory card which is removable. The Dimensions are 32 mm [height] x 24 mm [width] x 2.1 mm [thick] for an SD Card.}

RANDOM ACCESS MEMORY
Random access memory or RAM most commonly refers to computer chips that temporarily store dynamic data to enhance computer performance. By storing frequently used or active files in random access memory, the computer can access the data faster than if it to retrieve it from the far-larger hard drive. Random access memory is also used in printers and other devices.
Random access memory is volatile memory, meaning it loses its contents once power is cut. This is different from non-volatile memory such as hard disks and flash memory, which do not require a power source to retain data. When a computer shuts down properly, all data located in random access memory is committed to permanent storage on the hard drive or flash drive. At the next boot-up, RAM begins to fill with programs automatically loaded at startup, and with files opened by the user.
There are several different types of random access memory chips which come several to a "stick." A stick of RAM is a small circuit board shaped like a large stick of gum. Sticks of RAM fit into "banks" on the motherboard. Adding one or more sticks increases RAM storage and performance.
Random access memory is categorized by architecture and speed. As technology progresses, RAM chips become faster and employ new standards so that RAM must be matched to a compatible motherboard. The motherboard will only support certain types of random access memory, and it will also have a limit as to the amount of RAM it can support. For example, one motherboard may support dual-channel Synchronous Dynamic Random Access Memory (SDRAM), while an older motherboard might only support Single In-line Memory Modules (SIMMS) or Dual In-line Memory Modules (DIMMS).
Since random access memory can improve performance, the type and amount of RAM a motherboard will support becomes a major factor when considering a new computer. If there is a faster, better random access memory chip on the market, the buyer will want to consider purchasing a motherboard capable of using it. A year down the road, that 'new' RAM might be standard, while the buyer may be stuck with an old style motherboard. A new variety of non-volatile random access memory made with nanotubes or other technologies will likely be forthcoming in the near future. These RAM chips would retain data when powered down.
RAM varies in cost depending on type, capacity and other factors.

Personal Computer Buses
This is a subdivision of the main Interface Bus Tree for PC buses. This page provides descriptions for common PC expansion buses and peripheral buses. Interface Buses designed to operate with Personal Computers [PC's] are listed below. Some of these bus types may also operate over a back plane and or a cable. Each listing below has a brief description, use the link if provided for a more detailed description of the bus and to access links to component and IC manufacturers, connector pin outs, signal names, or specifications. The buses are used on IBM PC or Apple computers. A few SUN buses are also provided. Video buses operating over a cable between the computer and the monitor are listed all together near the bottom of the page, or may be found on a separate page, PC Video Monitor Buses. A table which compares many of the more common Personal Computer bus types is provided at the bottom of the page.
PC Cable & Slot Buses
AC97 {Audio Codec '97 interface specification defines audio and Modem functionality for PC systems. The AC97 standard is not really a bus. AC97 was developed by intel in 1997.}
Access Bus {Is a low speed serial bus aimed at the PC market for connecting peripheral devices. Access Bus is also used in the Display Data Channel [DDC] video standard for bi-directional communication between the video monitor and PC. Access.Bus uses the I2C bus as the electrical hardware interface. AccessBus uses a serial clock and serial data line operating at 100Kbps over a 10-meter cable}
ACR Bus {Advanced Communication Riser, another Computer OEM Riser specification. This latest version provides for modem support, LAN and xDSL support, and Audio support. ACR was preceded by CNR and AMR, both listed on this page. The ACR standard is backwards compatible with AMR. Additional description of Riser cards is also listed below.}
ADB Bus {Apple Desktop Bus was a serial bus used by Apple computer to drive the mouse and keyboard. The cable consisted of one data line [ADB], a power line [+5v] and a ground line. The maximum data rate was 125kbps. The ADB bus is OBSOLETE, replaced by the Firewire bus.}
AGP Bus {The Accelerated Graphics Port [AGP], is used as a Video Local bus on the Personal Computer. The AGP bus was derived from the Parallel PCI bus with a few additional signals. The AGP Bandwidth is 2.1GB/s. The PCI-Express card bus has replaced the AGP bus on personal computers.}
AIMM Bus {AGP Inline Memory Module [AIMM] defines a memory card that plugs into the AGP slot, on motherboards with an integrated graphics core [that don't require a Video card]. The AIMM card provides an additional 4MB of dedicated video memory. This interface solution is OBSOLETE.}
AMR Bus {Audio/Modem Riser specification defines a hardware scalable OEM PC mother board riser board and interface, which supports both audio and modem functions. An MR slot will provide a Modem function, while an AMR slot will provide both an Audio and Modem function. The modem is a WinModem. }
Apple Computer Buses {Apple and Macintosh [MAC] Computer Buses, pinout tables.}
AT Bus {ISA AT Computer Card Bus description. The PC-AT bus was replaced by the PCI bus. PCAT is OBSOLETE.}
ATA Bus {IDE/ATA Personal Computer [PC] Parallel Bus used as an interconnect between Mother boards and Hard drives, Disk drives, Floppy or CD drives. IDE: Integrated Drive Electronics, ATA: Advanced Technology Attachment. There is no difference between the IDE and ATA interface buses. The maximum bus speed is 133MBps, with a maximum ribbon cable of 18 inches.}
ATX Form Card Connector Pinout {The ATX Form Card was designed to up-grade the old AT form factor mother board to allow for ATX connectors. This turned out into translating a dual-pin header located on the AT motherboard into a connector on the rear I/O panel. This predates the defined I/O connectors on the ATX motherboard form-factor. The page provides the pinout for the ATX Form Card interface.}
ATX Mother Board Connectors {Different types of header connector pinouts for the PC ATX Mother Board standard}
ATX Riser Card {Riser card used with ATX form factor mother boards. The ATX Riser card allows compact PC chassis designs with out expansion slots, additional slots are added in the vertical direction by using the Riser card which contains the slot connectors~ A compact PC chassis may be used with an ATX Mother Board, or a larger chassis can be designed using the same Mother Board and a Riser card, providing expansion slots.}
Audio Codec 97 {AC97 interface specification defines audio and Modem functionality for PC systems. The latest version of the specification was released in 2002 as revision 2.3 of the spec.}
CardBay {Places the USB onto the PC Card PCMCIA format. CardBay was released in 2001, not sure it if ever caught on, but has been obsoleted by the ExpressCard release. Refer to the PC Card listing, version 8.0 combined the USB interface.}
CardBus {was a 32 bit, 33MHz PCMCIA Card. CardBus replaced the 16 bit PC Card version of the PCMCIA standard}
C-Bus {and C-Bus II were developed by Corollary Inc. as a multiprocessing chip set architecture used with motherboards with more then one linked processor [4-way and 8-way systems]. Corollary Inc. was purchased by Intel in 1997. This bus may no longer being implemented.}
Centronics Parallel Port {Pin Outs for the Personal Computer [PC] Bi-Directional Parallel Peripheral Interface, mainly used as a Printer Bus. The Centronics bus had a maximum cable limit of around 12 feet. Refer to the IEEE-1248 page which replaced the Centronics bus. The Centronics bus is OBSOLETE, replaced by IEEE-1248.}
CMR Bus {(Chaintech Mulmedia Riser) used on Chaintech Mother Boards as a Chaintech Multimedia Card expansion slot, based on CMC7.1. This may be their implementation of the CNR specification.}
CNR Bus {The Communication and Networking Riser Specification defines a hardware scalable Original Equipment Manufacturer (OEM) mother board riser and interface that supports the audio, modem, and local area network (LAN) interfaces of core logic chipsets. This standard does not support an expansion slot, but an OEM built in board to include the Motherboard connector [CNR Connector]. Supported interface buses include, AC '97, SMBus and USB including Power and a LAN interface. The board size and pinouts are also defined in the specification. Intel no longer produces CNR slots on its Pentium 4 Processor Motherboards.}
CompactFlash Card {Mass Storage removable Flash Memory card operates like an ATA drive using Flash memory. Devices are about 1/3 the size of a Type II PC Card}
DataFlash Card {Mass Storage removable Flash Memory card. One of a number of removable Flash Memory cards.}
Device Bay {A defined form factor peripheral which connects via USB and/or Firewire to the PC, but as of 2001 is not supported by Windows. The specification may be obtained from the 1394 Trade Association}
DIB {Dual Independent Bus architecture was developed by intel. The DIB consists of 2 buses, the processor to main memory interface [Front-Side Bus], and the L2 cache bus [Back-Side Bus]. The DIB interface allowed the processor to simultaneously access L2 cache and system memory or I/O. The DIB architecture was also used with AMD processors}
DVI Bus {The DVI [Digital Visual Interface] is a standard for high-speed, high-resolution digital displays}
EIA-232 Bus {EIA232 is the standard Serial Port interface [bus] used with personal computers. The maximum speed is rated at 20kbps, over a maximum cable distance of 20 meters. EIA-232 is the same standard as RS-232}
EISA {Extended Industry Standard Architecture [EISA] or Enhanced ISA bus: 8MHz @ 8/16/32 bits data bus, 32 bit address bus; PC Expansion Bus, compatible with ISA. An ISA card will work in an EISA slot, but an EISA card will not work in an AT slot. The EISA bus (in one mode) used both edges of the clock, with the rising edge used to output address, and the falling edge to place the data on the bus. Three other transfer modes were available. The EISA bus does not allow the board skirts common with the older XT cards. The EISA cards are the same physical size as the AT cards. The new address lines are termed "LA#", all address lines are latched. This bus is OBSOLETE and was replaced by the PCI and AGP buses. This page provides additional data on pin-out, signal names and board sizes; EISA PinOut}
Embedded PCI-X Specification {[ePCI-X], The PICMG 1.2 specification defines the mechanical and electrical interface to support a standard form factor PCI computer system with either two PCI/PCI-X busses or a single PCI/PCI-X bus. The document also defines the electrical and mechanical connections for a single board computer and backplane. This is an upgrade to the PCI-ISA specification. PCI-X capabilities are added to the PCI bus and the ISA bus is replaced by a second PCI-X bus, on the PCI-ISA backplane. The board retains the same mechanical dimensions as PCI-ISA but the components move to the PCI side and the slot occupies a PCI position on a backplane. Also refer to the PCI-ISA listing, or the PCI listing}
ePCI-X {Defined in the Embedded PCI-X listing.}
Ethernet Bus {The Ethernet Bus Standard is used as a Local Area Network [LAN]. The normal implementation is over a coax or twisted pair cable at either 10Mbps or 100Mbps}
Expansion_Buses for the Personal Computer.
ExpressCard {PCMCIA ExpressCard "Newcard" is the new form factor for PCMCIA Circuit Cards and will utilize either USB and PCI Express buses. The new single width card is 34mm x 75mm. The double width card is 54mm x 74mm (has a 22mm notch). The single card is called ExpressCard/34, and the double width card is called ExpressCard/54. Both cards are 5mm high.}
Fiber Channel {Used for transferring data to workstations, mainframes, supercomputers, desktop computers, storage devices, displays and peripherals [high-end server SANs]. Fibre Channel operates over fiber [400MBps] or copper [100MBps] cables}
FireWire Bus {The IEEE 1394 [FireWire] Bus, used as a high-speed serial bus between a PC and peripheral device}
Flash Memory Card buses There are a number of Flash memory card formats listed on this page, under their common standard or specification name. Flash Memory Card types include: SD Card, CompactFlash, SmartMedia...
Floppy Drive Bus {Pin Out Table}
Gigabit Ethernet {operates using either Shielded Twisted Pair [STP] copper, Un-Shielded Twisted Pair [UTP], or CAT-5 copper or fiber cable. Gigabit Ethernet also runs over a backplane at over 1GHz.}
GPA Bus {Graphics Performance Accelerator [GPA] defines a memory card that plugs into the AGP slot on mother boards with an integrated graphics core [don't require a Video card]. The AIMM card provides an additional 4MB of dedicated video memory. The previous name for this interface was AGP Inline Memory Module [AIMM]}
HD Audio {The new PC audio codec standard replacing AC97}
Hard-Drive buses {[before ATA or IDE] used to interface with hard drives include: XTA, ST506, and ESDI. XTA [XT Attachment] - Is a rarely used implementation of the ATA Interface that used an integrated 8 bit XT controller. ESDI [Enhanced Small Device Interface], was considered a successor to ST506/412 with faster transfer rates and supporting larger drive sizes. The ESDI bus used the same two-cable connection as the ST506. These interfaces are OBSOLETE and replaced by the ATA (IDE) bus.}
HTX Slot {Also called the HT slot for EATX server motherboards using HyperTransport Daughtercards}
HyperTransport Bus (A Point-to-Point bus with [at least] two unidirectional links; Uses 2, 4, 8, 16 or 32 bits [in each direction] with a data rate of 800Mbs/per pair with a 400MHz clock. Formally known as Lightning Data Transport (LDT). Used in mobile personal computers, servers, network equipment, embedded applications, and communications equipment)
IDE Bus {IDE/ATA Personal Computer [Parallel] Bus used for Hard drives, Floppy and CD drives. The Integrated Drive Electronics [IDE] bus, which is a 16-bit parallel interface, is being replaced by the Serial ATA bus [SATA]. The last version of the IDE bus [ATA-7] runs at 133MBps over an 18 inch ribbon cable.}
ISA/AT Bus {IBM Compatible ISA AT bus: 8MHz @ 8 and 16 bits data bus, 24 bit address bus, +/- 12 volts, +/- 5 volts, 15 Interrupt lines. The standard drive level is 24mA for all non-Open Collector signals on the bus. The AT card used the standard (edge) connector provided by the XT bus and added an additional (edge) connector behind that with the same pin-spacing @ 0.1 inch center-to-center. The additional connector has only 38 (19 per side) fingers, while the XT connector had 62 (32 per side) fingers. The Mother Board could then accept either an 8 or 16 bit card in an 8 bit slot (XT), or (if the connector was provided) a 16 bit card in an AT slot. The additional connector provided 4 additional address lines, and 8 additional data lines. The ISA AT bus is OBSOLETE, replaced by the PCI bus.}
ISA/XT Bus {IBM Compatible ISA XT bus: Obsolete; 4.77MHz @ 8 bits, +/- 12 volts, +/- 5 volts. The XT bus used a 62 pin (.1" center) edge connector; 31 pins per card side. Used a single oscillator of 14.31818MHz which was divided by 3. 8 Data lines, 0 to 7 (LSB=0). 20 Address lines, 0 to 19 (LSB=0). 1 Clock line (4.77MHz). 1 Reset line, 8 Interrupt lines. Some 8 bit cards have skirts which extend the board below the depth of the top of the connector to allow additional circuitry. These cards, with skirts, are not compatible with the 16 bit AT bus. The XT bus uses connector J1 (A/B), AT uses J1 (A/B), J2 (C/D). The ISA XT bus is OBSOLETE, replaced by the ISA AT bus.} This page lists the PC XT Bus pinout
IEEE-1284 {Personal Computer [PC] Bi-Directional Parallel Peripheral Interface, mainly used as a Printer Bus, and a general purpose Parallel Peripheral Interface.}
iLink { is Sony's name for FireWire, i.Link is based on IEEE-1394 using conventional metallic conductors.}
JBus {developed by Sun for its computers, is a 128 bits wide bus, at 200MHz [with three loads], and features 16 to 64 Gbytes/s on-chip. However, JBus delivers only 3.2 Gbytes/s when used as an off-chip bus.. JBus uses 170-pins on a 300-pin connector. JBus uses 1.5volt DTL [Dynamic Termination Logic] devices.}
Joystick Interface Bus { The Joystick port used with Personal Computers uses a 15pin D connector and has the following pin out: Pin 1; +5Vdc, Pin 2; Joystick/A Right Button, Pin 3; Joystick/A X-Coordinate, Pin 4; Ground, Pin 5; Ground, Pin 6; Joystick/A Y-Coordinate, Pin 7; Joystick/A Left Button, Pin 8; +5Vdc, Pin 9; +5V dc, Pin 10; Joystick/B Right Button, Pin 11; Joystick/B X-Coordinate, Pin 12; MIDI Out, Pin 13; Joystick/B Y-Coordinate, Pin 14; Joystick/B Left Button, Pin 15; MIDI In}
Keyboard Interface Bus {The serial Keyboard used on Personal Computers [PCs] is a [PS/2] 6 pin Circular DIN. The pin-out for the Keyboard or Mouse port is: Pin 1; Data, Pin 2; Reserved, Pin 3; Ground, Pin 4; +5 Vdc, Pin 5; Clock, Pin 6; Reserved. Another variant may be seen as a 5-pin DIN; using Pin 1; Clock, Pin 2; Data, Pin 3; Reserved, Pin 4; Ground, Pin 5; +5 volts. Some newer computers may have USB ports [listed below] to handle this function}
LPT {port, [line printer terminal] an old term which now refers to a parallel port interface. The two main parallel port interfaces include the Centronics interface or the IEEE 1284 interface. Both interfaces are listed on this page. The parallel port is slowing it's age and in some cases may be replaced by an USB interface or Ethernet port.}
Macintosh Computer Buses {Apple and Macintosh [MAC] Computer Buses; Connector Pin-Outs only}
MCA {Micro Channel Architecture bus: Designed to correct the problems with the ISA bus, but never caught on out side of IBM machines. The bus is Obsolete and was later replaced by the PCI bus.; 10MHz @ 16 or 32 bits, uP independent, asynchronous, IBM proprietary on PS2 computers. With bus enhancements the speed reaches 80MBps, using clock doubling.}
Memory Stick Flash {Memory Stick Flash is another flash memory card format type. The device size is 50 mm x 21 mm x 2.8 mm}
MIDI Interface Bus {[Musical Instrument Digital Interface] uses a 5-pin circular DIN connector. There are three different pinouts for; MIDI In, MIDI Out, and MIDI Thru. The MIDI signals are also found on the on a standard sound card Joystick/MIDI 15-pin connector. MPU401: [MIDI Processing Unit 401], Developed by Roland. }
Mini PCI {Is a small form factor version of a PCI card. Mini PCI uses a subset of the PCI specification, and is electrically identical to the Peripheral Component Interface. Mini PCI uses a 32 bit data bus running at 3.3v. The board uses 124-pin fingers. There are Type I and Type II, and Type III daughter-boards. Dimensions [General] for a Type IIIA are 59.75 mm x 50.95 mm x 5mm. Mini PCI was designed for the NoteBook/ Laptop market, i.e mobile systems.}
Mini PCI Express {Is a small form factor version of a PCI Express card. Mini PCI Express was designed for the NoteBook/ Laptop market, i.e mobile systems. The board size is 51mm x 30mm. More Mini PCI EXpress cards can fit within a Lap-top because they are about half the size of a Mini PCI board.}
Miniature Card {Miniature Card is a smaller implementation of PCMCIA. Miniature Cards dimensions: 3.5mm x 33mm x 38mm (TxLxW). The electrical specifications are a subset of the PC Card standard, restricted to memory applications only. It uses a 16-bit data bus and a 24-bit address bus to allow a single card to store up to 64MB.}
Mouse Interface Bus {The serial mouse used on Personal Computers [PCs] is a 6 pin Circular DIN. The pin-out for the Keyboard or Mouse port is: Pin 1; Data, Pin 2; Reserved, Pin 3; Ground, Pin 4; +5 Vdc, Pin 5; Clock, Pin 6; Reserved. As of mid 2005 some computers are shipping without this interface, favoring a USB connection instead.}
Modem Interface Bus {A listing of International Telegraphic Union Modem standards}
Mother Board Types {A listing of different Mother Board types and their sizes; ATX and EBX for example, many others listed}
Multimedia Card {Multimedia Card [MMC] is another flash memory card format type. The device size is 32 mm x 24 mm x 1.4 mm}
NUbus {IEEE Std 1196-1987 Simple 32-Bit Backplane Bus; NuBus. An Apple [Macintosh and NeXT Computer] expansion bus with 32 bit address and 32 bit data bus operating at 10MHz, with a throughput of 40MBps. The card had a form factor of 12" x 7", and used a standard 96-pin three-row (VME) connector. NuBus90, increased the clock rate to 20Mhz providing a throughput of 70Mbps. Nubus is OBSOLETE, replaced by the PCI bus.}
OP iLink {Sony's name for FireWire; OP i.Link is based on IEEE1394a-2000 using single-core plastic optical fiber.}
PATA Disk Drive Bus {The un-official name for IDE/ATA Personal Computer [Parallel] Bus used for Hard disk drives, Floppy and CD drives. The Integrated Drive Electronics [IDE] bus is a 16-bit parallel cable interface, replaced by the Serial ATA bus [SATA]. The last version of the IDE bus [ATA-7] runs at 133MBps over an 18 inch ribbon cable.}
PC Bus {XT, AT, ISA, and EISA Computer Card Bus descriptions, all were replaced by the PCI bus. These buses are OBSOLETE.}
PC/104 Bus {PC/104 Bus is used as an embedded PC bus, combining the IBM compatible ISA buses; XT, and AT buses into a different form factor [Card size]. The boards stack on top of each other. PCI/104-Plus introduces the PCI bus, and PCI/104 removes the IBM PC XT and AT buses leaving only the PCI in an embedded form factor. The IBM 4MHz XT bus width of 8 bits, along with the 16 bit AT bus is used in another card size. The PCI/104-Plus specification added the 33MHz PCI bus. The PCI-104 standard also relates to the 33MHz PCI bus, but removes the ISA buses. The standard does not support 66MHz PCI.}
PCI Bus {The Peripheral Component Interface 'PCI' [Parallel] Bus was originally developed as a local bus expansion for the PC. The first version of the PCI bus ran at 33MHz with a 32 bit bus (133MBps), the current version runs at 66MHz with a 64 bit bus. The PCI bus operates either synchronously or asynchronously with the "mother Board bus rate: The page contains the PCI connector Pin-Outs}
PCI-X Bus {The Peripheral Component Interface [PCI-X] addendum is an enhancement to the current 64 bit 66MHz PCI bus specification. The minimum clock speed for PCI-X is 66MHz [PCI-X 66]. Additional bus speeds include: PCI-X 133, PCI-X 266 and PCI-X 533 providing up to 4.3GBps [PCI-X 1066 in the works]. PCI-X is backwards compatible with PCI. I believe the X stands for extension}
PCI Express Bus {Serial PCI Bus uses two low-voltage differential LVDS pairs, at 2.5Gb/s in each direction. Using 8B/10B encoding, and Supporting 1x, 2x, 4x, 8x, 12x, 16x, 32x bus widths. Set to replace the Parallel PCI bus; PCI, and PCI-X. PCIe is currently replacing the AGP slot on PC Mother Boards.}
PCI-ISA {A passive backplane which moves all active devices off the motherboard and onto a single card. The controller card used in the system has fingers [edge connectors] for both PCI and the ISA bus, the Mother Board only connectors. This allows additional cards to be added to the mother board which use either the ISA or PCI buses. Because only connectors reside on the mother board, repair time is increased, and down time is decreased. The standard is PICMG 1.0. The specification is used in embedded or industrial computer systems. A similar standard is PISA listed below. A newer standard called ePCI-X removes the obsolete ISA bus and replaces it with PCI-X interfaces.}
PCMCIA PC Card {Implementation of the 16 bit ISA Bus on a PCMCIA card: which is used as a removable card to supply storage or other functions to a PC. See Cardbus as an up-grade option.}
PCMCIA Cardbus {Implementation the 32 bit PCI bus in a PCMCIA form factor: which is used as a removable card to supply storage or other functions to a PC}
PCMCIA Miniature Card {Miniature Card is a smaller implementation of PCMCIA. Miniature Cards dimensions: 3.5mm x 33mm x 38mm (TxLxW). The electrical specifications are a subset of the PC Card standard, restricted to memory applications only. It uses a 16-bit data bus and a 24-bit address bus to allow a single card to store up to 64MB.}
PCMCIA ExpressCard {ExpressCard "Newcard" is the new form factor for PCMCIA Circuit Cards and will utilize either USB and PCI Express buses. The new single width card is 34mm x 75mm. The double width card is 54mm x 74mm (has a 22mm notch). The single card is called ExpressCard/34, and the double width card is called ExpressCard/54. Both cards are 5mm high.}
PictBridge {provides print services between devices like printers and digital cameras. The PictBridge standard is CIPA DC-001 and uses USB as the physical layer.}
PISA Bus {PC Expansion Bus [PCI + ISA]: A normal ISA card with an additional row of pins above the ISA pins. The new row of pins are used for the PCI bus. This card is normally only found in OEM industrial or embedded computers. the PISA standard was developed by Kontron. PISA is a combination ISA, and PCI bus in a short card form factor. In PISA's case the ISA and PCI fingers are on top of each other (but offset). You need a back plane designed to accept PISA cards, to use the PISA card. The PISA bus is used as an Industrial Embedded Computer Bus, not a consumer Personal Computer bus. A similar bus standard from PICMG uses both ISA and PCI interfaces but the pins [fingers] reside one after the other, not over top each other. PICMG 1.0 defines the PCI-ISA Card Edge Connector for Single Board Computers. A newer standard called ePCI-X removes the obsolete ISA bus and replaces it with PCI-X interfaces ~ PICMG 1.2.}
PISA express Bus {PC Expansion Bus [PCI + PCie]: modeled after the PISA Form Factor. The bus supports a maximum of two PCIe x1 slots, one PCIe x4 slot, one PCIe x16 slot, three PCI slots, one LPC bus, and two Express cards, the company says. Additionally, the standard includes power connections compatible with ATX and BTX motherboard standards. This card is normally only found in OEM industrial or embedded computers. Developed by Kontron}
QuickRing Bus {QuickRing, is an offshoot of SCI. QuickRing uses six data signals and a clock speed of 175 MHz to achieve a throughput of 200 MBytes/second/link. The six data signals use the SCI P1596.3 Low Voltage Differential Signaling (LVDS) protocol for low power dissipation and low noise immunity. The QuickRing Bus is OBSOLETE, replaced by the PCI bus}
RapidIO {RapidIO is used in High-performance embedded applications such as networking, storage, multimedia, and signal processing. RapidIO uses LVDS}
Reduced Size Multimedia Card {Reduced Size Multimedia Card [RS-MMC] is another flash memory card format type, the smaller version of MMC. The device size is 24 mm x 16 mm x 1.4 mm}
Riser Cards {Personal Computer Expansion Bus Riser Board standards include: ACR [Advanced Communication Riser], AMR [Audio/Modem Riser], and CMR [Communication and Networking Riser]. Each Riser standard has a listing on this page which may provide additional technical information about the standard. The Riser approach is designed to bring the basic wiring and control of a function to a riser slot [and board] so the function may be implemented with minimal cost off the Mother Board ~ with out the need for a PCI interface, for example. Computer OEM's [Original Equipment Manufacturers] would use a Riser slot [and board] to deliver a modem function at minimal cost.}
Riser Board {There is a secondary definition of Riser Card. In this case a Riser card is an 'extender' board which plugs into an expansion card slot. The extender rises up out of the slot to expose one or more identical bus slots (PCI-Express for example). These new slot connectors accept cards in the Horizontal direction. So a Mother Board which would have taken an expansion card in the vertical direction now because of the Riser Board allows cards to be Horizontal to the Mother Board. The link to Riser Boards points to OEM [Original Equipment Manufacturers] Card Manufacturers. This type of Riser Board is also listed on this page as an ATX Riser Board}
RS-232 Bus {RS232 is the standard Serial Port interface [bus] used with personal computers. The maximum speed is rated at 20kbps, over a maximum cable distance of 20 meters.}
S-100 Bus {Obsolete interface bus.}
SATA Bus {Serial ATA is the new four-wire Mother Board to Hard Disk Drive serial data bus, replacing the IDE [Parallel ATA] bus standard. Serial ATA uses only 4 signal pins, improving pin efficiency over the IDE interface which uses 26 signal pins going between devices [over an 80 conductor ribbon cable onto a 40 pin header connector]. The 4 lines are used for transmitting and receiving differential pairs, plus an additional three grounds pins and a separate power pin.}
Sbus {[IEEE-1496] is a computer expansion card bus used for Sun workstations. Sbus used a 32 bit address and data bus which run at 25MHz for data transfers of 100Mbps. Later increased to two 32 bit word transfers for a through-put of 200Mbps. Sbus is OBSOLETE, I think, replaced by the PCI bus. Note: Sun computer buses seem to mimic PC buses at this point.}
SCI Bus {Scalable Coherent Interface}; IEEE Std 1596-1992, SCI is a scalable network, nodes are interconnected in a point-to-point unidirectional link [ring]. The bandwidth grows with the number [concurrent] nodes used. SCI links are operate at 1 Gbps [serial], or 1 GBps [16-bit parallel], using a 250-MHz bi-phase clock over fiber optic or twisted-pair wires. Physical SCI controllers use LVDS signaling levels for 16 and 8 bit wide links.}
SCSI Bus {Small Computer Systems Interface [SCSI] is used as a 8 or 16-bit parallel interface used to attach peripheral devices to the PC. The latest version runs at 320MBps. SCSI was always much more expensive then IDE buses; how ever parallel SCSI is being replaced by Serial SCSI, listed below.}
SD Card {[Secure Digital] Card. A stamp-sized flash memory card which is removable. The Dimensions are 32 mm [height] x 24 mm [width] x 2.1 mm [thick] for an SD Card. While the miniSD Card is only 21.5 mm [height] x 20 mm [width] x 1.4 mm [thick]}
SDIO Card {[Secure Digital I/O] Card. A stamp-sized flash memory card which is removable. The Dimensions are 32 mm [height] x 24 mm [width] x 2.1 mm [thick] for an SD Card.}