Amiga 3000 PC Desk-top

Personal Computer Buses


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 developed by intel in 1997, is not really a bus.}

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. 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 5v power line and a ground line. The maximum data rate was 125kbps. The ADB bus is OBSOLETE, replaced by Firewire bus.}

AGP Bus {The Accelerated Graphics Port [AGP], is used as a Video Local bus on a 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 PCs.}

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.}

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.}

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.}

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 PC Card, 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.}

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. 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. 1 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.}

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. EISA is OBSOLETE, replaced by the PCI and AGP buses. 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.}

ESDI;(Enhanced Small Device Interface) A 20M Byte hard drive interface that pre-dated ATA. OBSOLETE

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.}

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}

MC-10 {Obsolete serial interface based on RS232, used on the TRS-80}

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.}

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}

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.}

Serial ATA Bus {SATA; The new four-wire Mother Board to Hard-drive serial data bus, set to replace the IDE [Parallel ATA, PATA] bus standard. Serial ATA uses only 4 signal pins, improving pin efficiency over the parallel ATA 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.}

Serial SCSI Bus {Serial Attached SCSI [SAS] uses the SCSI protocol with a Serial ATA physical interface, running at 1.5Gbps or 3.0Gbps. SAS may soon replace parallel SCSI}

Serial Storage Architecture Bus {The 'SSA' spec defines the physical medium, to include [TTL] differential drivers/receivers, clocking, connectors and cables. Runs in full duplex with 20MBps transfer rate in each direction [40MBps]. At that rate the maximum distance is 680 meters. ~ OBSOLETE.}

SIOM {[Server I/O Module], a new form factor module using PCI Express. The module consists of a PC board surrounded by a metal can. The module comes in two widths, single wide and double wide. Both module form factors have the same height and depth, only the width changes. The modules connect to a mother board via fingers on the PWB. The single wide modules support x8 and the double wide modules support x16 PCIe lanes.}

SmartCard Bus {ISO 7816; Defines a plastic 'chip card' used to store data via a magnetic strip}

SmartMedia {SmartMedia is another flash memory card format type. The device size is 45 mm x 37 mm x 0.76 mm Cards operate using either 3.3 volt or 5 volt.}

S/PDIF bus {[Sony/Philips Digital Interface] used for Digital Audio information transfer. The Audio is transmitted from the computer by either an RCA connector, or Fiber optic connectors. The connectors are in pairs, one input and one output. The S/PDIF interface is similar to the AES3 interface}

SSFDC Bus {[Solid State Floppy Disk Card], is a Removable NAND-type small flash memory card [45mm x 37mm x 0.76mm and lightweight, 2g]. Developed by Toshiba Corp. SSFDC is the old name for SmartMedia}

USB Bus {The Universal Serial Bus provides two-way communication between the PC and peripheral devices, over a Differential serial interface cable. A Slow-Speed mode of 1.5Mbps is used for devices such as mice. Full-Speed mode is used by most devices and allows a transfer rate of 12Mbps. High-Speed mode [defined by USB 2.0] allows rates of 480Mbps.}

VLB {VESA [Video Electronic Standards Association] Local bus [VLB or VL-Bus]: 33MHz @ 16/32 data bits, 30 address bits; PC Local Bus Expansion. A maximum of 3 devices may be connected to the bus. The VLB resides on a standard 16bit ISA card with the additional pins required by the VLB interface residing after the ISA pins, allowing an ISA card to use the same slot. The VLB bus is now obsolete.}

WFF {[Wireless Form factor] another PCI Express form factor card designed for laptop computers. The Wireless Form factor card is around the same size as a miniPCI card.}

Wireless USB

Zorro II {An IBM PC form factor card and backplane interface used with the Commodore Amiga 2000 computer in the mid 1980s. Using a 16 bit data bus.}

Zorro III {A General Purpose Expansion Bus for High Performance Amiga Computers released in the early 1990's [Commodore computers]. The specification defined both the physical card size and the electrical interfaces to the card. The interfaced seems to based on the Motorola 680x0 processors [68000 processor], using a full 32 bit address bus and 32 bit data bus. Bus speed was independent of the host board. The Zorro III card was backward compatible with a Zorro II card. Side note Commodore went bankrupt in 1994, so interface bus has not been used for a number of years now.}




PC Video Cable Interfaces

MDA [Monochrome Display Adapter]: established by IBM as part of the original Personal Computer [PC]. MDA is a monochrome-only, text-only standard, allowing text display at 80x25 characters. OBSOLETE.

CGA [Color Graphics Adapter]: The CGA standard [1981] supports several different modes; the highest quality text mode is 80x25 characters in 16 colors. The monitors are digital with a composite signal which is at TTL logic levels; Hs, Vs, and RGBI all at TTL logic levels. OBSOLETE.

EGA [Enhanced Graphics Adapter]: This EGA standard [1984] offered improved resolutions and more colors than CGA. EGA allowed graphical output up to 16 colors (chosen from a palette of 64) at screen resolutions of 640x350, or 80x25 text with 16 colors, all at a refresh rate of 60 Hz. The monitors have a digital interface. OBSOLETE. The link provides the Pin Outs for the connector.

VGA [Video Graphics Array]: VGA [1987] is a superset of EGA, incorporating all EGA modes. Older displays sent digital signals to the monitor, while VGA (and later) send analog signals. This change was necessary to allow for more color precision. VGA pinout listing is provided.

XGA [Extended Graphics Array]: Introduced in 1990 by IBM.

SVGA [Super VGA] offers more colors and resolutions; However, SVGA really does not exist as a single standard. The primary standard refers to the BIOS, and how the computer talks to the monitor. VESA Display Data Channel [DDC] is a VESA standard that defines how to read certain pins in a standard SVGA monitor to query the monitor's capabilities.

FPDI-1 [Flat Panel Display Interface] describes the electrical, logical, and connector interface between flat panel displays and display controllers in an integrated environment.

P&D [Plug and Display] provides a Digital interface and an optional Analog interface. DDC2 is provided in addition to an optional USB and/or FireWire.

DFP [Digital Flat Panel] connector pin-out and signal names. DFP is based off the Plug and Display [P &D] interface

EVC [Enhanced Video Connector] connector pin-out and signal names

VMChannel [VESA Media Channel] describes a hardware interface for desktop multimedia systems. The VMChannel is a multiple master, multiple drop, clock synchronous interface designed for concurrent pixel data streams. VMChannel enables the real time flow of uncompressed multimedia pixels in a bidirectional fashion between multiple video adapters.

13W3 video interface normally found with Sun Computers.

SGI Bus [Silicon Graphics Inc] produced work-stations, a few pinout tables are listed on this page.
9-Pin Digital Video
DB-15 Video Interface
Flat Panel Digital Video & SGI O2Cam Video Interface Pinout


PC Interfaces Comparison




IBM compatible computer buses, Macintosh computer buses, and SGI bus interfaces are listed above. In most cases the backplane or motherboard will provide slots to add additional cards to the system. The additional slots are called expansion slots. The actual number and type of expansion slots will vary with different mother boards. How ever some reduced cost systems shipped with no expansion slots at all. But the real number of maximum expansion slots will depend on the interface bus used. For example the ISA bus; PC-XT and PC-AT buses could have a maximum number of 8 expansion slots. Once a particular bus begins to become obsolete, it's vary common for the mother board to provide two or more different slots. For example as the ISA slot was becoming obsolete, a mother board might ship with a number of PC-AT slots, a few PCI slots, and an AGP slot.

All of the different Personal Computer [PC] interface bus descriptions or links to electronic bus pages listed above deal with layer 1 [Physical, Electrical and Mechanical Layer] of the OSI protocol stack. Many electronic bus pages also reference layer 2; the Data Link Layer [which provide bit/byte stuffing, checksum, Protocols..]. In addition, all of the page links listed above provide links to devices related to that particular bus, which include IC manufacturers, Connector manufacturers, Bus Termination manufacturers, cable manufacturers, and electronic equipment manufacturers, Standards/Specifications and so on... The extent of the description provided for any particular electronic bus varies widely from page to page depending on the bus. In only a few occasions is a particular bus listed as Obsolete; however, there may be many buses listed, if not obsolete, that should not be used for new designs.

Cable and Back Plane PC Bus Standards [Truncated] Computer Buses
Bus Data Rate Type Description Topology Voltage Coax Twisted Pair
RS-232 19.2 Kbps Unbalanced 20 meters, Single Ended Point-to-Point ~ 5V 15 or 25 pin cable
AccessBus 100 Kbps Unbalanced Similar to I2C, 10 meter Multi-Point ~ 5V 4 wire,Data/Clk/V/GND
I2C Bus 3.4 Mbps Unbalanced 2 Wire, 1 Data, 1 Clk-Access Bus Multi-Point ~ TTL PWB
SMBus 100 KHz Unbalanced 2 Wire, based on I2C/Access Bus Multi-Point TTL Undefined
10Base2 10 Mbps Unbalanced 183 meters, IEEE-802 Thin Net Multi-Point ECL 50W ------
10Base5 10 Mbps Unbalanced 500 meters, IEEE-802 ThickNet Multi-Point ECL 50W ------
10Base-T 10 Mbps Balanced 100 meters, Category 3 cable Multi-Point ECL ------ STP or UTP
100Base-T 100 Mbps Balanced 100 meters, Category 5 cable Multi-Point +/- 1.0v ------ STP or UTP
RapidIO 10 Gbps Balanced Differential LVDS Star / Mesh LVDS Back Plane or Cable
HyperTransport 800Mbps/bit pair Balanced 2/4/8/16/32 bits Daisy-Chained LVDS PWB
FireWire, 1394b 800 Mbps Differential "...." 1394b Point-to-Point 0.6~0.8V 2 pairs of STP & 2 Power
USB 480 Mbps Differential USB 2.0 Star Topology 0.3~3.6V ------ STP
ATA-7 133 Mbps 16 Bits Ultra ATA/133,Added CRC Chained TTL 80 pin ribbon/40 connect
Serial ATA 150MBps Differential 2 differential pairs [Tx/Rx] Point-to-Point LVDS 4 conductor cable
SCSI-3 40 MBps 8 / 16 Bit "..", 16 devices Chained TTL 50 or 68 pin connector
Ultra 640 SCSI 640 MBps 32 Bit "..", 4 devices Chained TBD Differential
PC-AT (ISA) 8MHz 16 Bits Personal Computer Bus Card edge TTL Obsolete
EISA 8MHz 32 Bit PC local bus Card edge TTL Obsolete
Micro Channel 10MHz 32 Bits Personal Computer Bus Card edge TTL Obsolete
VESA (VLB) 33MHz 32/64 Bit PC local bus Card edge TTL Obsolete
PCI 33/66MHz 32/64 Bits Chip-to-Chip, Multidrop PC Local Bus Card edge TTL Computers
PC Card 8MHz 16 Bit ISA in a PCMCIA form factor Connector-ized TTL Computers
CardBus 33MHz 32 Bit PCI in a PCMCIA form factor Connector-ized PCI Computers
AGP 8x 533MHz 8/16/32 Bit "....." 2.1GB/s Point-to-Point TTL AGP Bus
PCI Express 2.5Gb/ps up to 32 Bits Serial PCI, differential pairs Point-to-Point LVDS Differential Pair

The table above only gives the final version for each of the PC interfaces shown.
The full table which also shows a number of previous bus versions is listed on the PC Buses Comparison Table page.


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Modified 1/26/12
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