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PCI
Peripheral Component Interconnect

Five 32-bit PCI expansion slots on a motherboard
Year created:July 1993
Created by:Intel
Superseded by:PCI Express (2004)
Width:32 or 64 bits
Number of devices:1 per slot
Capacity133 MB/s
Style:Parallel
Hotplugging?no
External?no
64-bit PCI expansion slots inside a Power Macintosh G4
64-bit PCI expansion slots inside a Power Macintosh G4

The Peripheral Component Interconnect, or PCI Standard (in practice almost always shortened to PCI), specifies a computer bus for attaching peripheral devices to a computer motherboard. The range of Integer values that can be stored in 32 bits is 0 through 4294967295 or −2147483648 through 2147483647 using Two's complement encoding A motherboard is the central or primary Printed circuit board (PCB making up a complex electronic system such as a modern Computer or Laptop Not to be confused with PCI-X, a different bus architecture Peripheral Component Interconnect Express, officially abbreviated as PCI-E A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication In Telecommunication and Computer science, parallel communication is a method of sending several data signals simultaneously over a communication link (comprising '64-bit' CPUs have existed in Supercomputers since the 1960s and in RISC -based workstations and servers since the early 1990s. The Power Mac G4 is a series of Personal computers that was designed manufactured and sold by Apple between 1999 and 2004. In Computer architecture, a bus is a subsystem that transfers data between computer components inside a Computer or between computers For an account of the words periphery and peripheral as they are used in biology sociology politics computer hardware and other fields see the A computer is a Machine that manipulates data according to a list of instructions. A motherboard is the central or primary Printed circuit board (PCB making up a complex electronic system such as a modern Computer or Laptop These devices can take any one of the following forms:

The PCI bus is common in modern PCs, where it has displaced ISA and VESA Local Bus as the standard expansion bus, but it also appears in many other computer types. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated Industry Standard Architecture (in practice almost always shortened to ISA) was a Computer bus standard for IBM compatible computers The VESA Local Bus (usually abbreviated to VL-Bus or VLB) was mostly used in personal computers The bus is being succeeded by PCI Express, which launched in 2004 and offers much higher bandwidth. Not to be confused with PCI-X, a different bus architecture Peripheral Component Interconnect Express, officially abbreviated as PCI-E As of 2007 the PCI standard is still used by many legacy and new devices that do not require the higher bandwidth of PCI-E. New computers are also still provided with ample PCI slots.

The PCI specification covers the physical size of the bus (including wire spacing), electrical characteristics, bus timing, and protocols. The specification can be purchased from the PCI Special Interest Group (PCI-SIG). The PCI-SIG or Peripheral Component Interconnect Special Interest Group is an electronics industry consortium responsible for specifying the Peripheral Component Interconnect

Typical PCI cards used in PCs include: network cards, sound cards, modems, extra ports such as USB or serial, TV tuner cards and disk controllers. A Network card, Network Adapter, LAN Adapter or NIC (network interface card is a piece of Computer hardware designed to allow computers A sound card (also known as an audio card is a Computer Expansion card that facilitates the input and output of audio signals to/from a computer under Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information In Computing, a serial port is a Serial communication physical interface through which information transfers in or out one Bit at a time (contrast A TV tuner card is a computer component that allows Television signals to be received by a Computer. The disk controller (or "hard disk controller" is the circuit which allows the CPU to communicate with a Hard disk, Floppy disk or In years past video cards were mounted using PCI, but rapidly outgrew the capabilities of PCI, so that today PCI video cards are a rare low-end option. A video card, also known as a graphics accelerator card, display adapter, or graphics card, is a hardware component whose function is to Many common PCI card devices are now integrated into motherboards, so that modern PCs often have no cards fitted. PCI is still used for many specialized cards, although USB is replacing that purpose also.

Contents

History

Work on PCI began at Intel's Architecture Lab circa 1990. Intel Architecture Labs, also known as IAL, was the Personal Computer system research and development arm of Intel Corporation during the 1990s PCI 1. 0, which was merely a component-level specification, was released on June 22, 1992. Events 217 BC - Battle of Raphia: Ptolemy IV of Egypt defeats Antiochus III the Great of the Seleucid kingdom. Year 1992 ( MCMXCII) was a Leap year starting on Wednesday (link will display full 1992 Gregorian calendar) PCI 2. 0, which was the first to establish standards for the connector and motherboard slot, was released on April 30, 1993. Events 313 - Roman emperor Licinius unifies the entire Eastern Roman Empire under his rule Year 1993 ( MCMXCIII) was a Common year starting on Friday (link will display full 1993 Gregorian calendar) PCI 2. 1 was released on June 1, 1995. Events 193 - Roman Emperor Didius Julianus is Assassinated 987 - Hugh Capet is elected Year 1995 ( MCMXCV) was a Common year starting on Sunday. Events of 1995

PCI was immediately put to use in servers, replacing MCA and EISA as the server expansion bus of choice. Micro Channel Architecture (in practice almost always shortened to MCA) was a proprietary 16- or 32-bit parallel Computer bus The Extended Industry Standard Architecture (in practice almost always shortened to EISA and frequently pronounced "eee-suh" is a bus standard for IBM compatible In mainstream PCs, PCI was slower to replace VESA Local Bus (VLB), and did not gain significant market penetration until late 1994 in second-generation Pentium PCs. The VESA Local Bus (usually abbreviated to VL-Bus or VLB) was mostly used in personal computers By 1996 VLB was all but extinct, and manufacturers had adopted PCI even for 486 computers. The Intel 486, otherwise known as the 80486 i486 or just 486 was the first tightly pipelined X86 design [1] EISA continued to be used alongside PCI through 2000. Apple Computer adopted PCI for professional Power Macintosh computers (replacing NuBus) in mid-1995, and the consumer Performa product line (replacing LC PDS) in mid-1996. Apple Inc, ( formerly Apple Computer Inc, is an American Multinational corporation with a focus on designing and manufacturing Consumer electronics Power Macintosh, later Power Mac, is a line of Apple Macintosh Workstation -class Personal computers based on various models of PowerPC NuBus is a 32-bit parallel Computer bus, originally developed at MIT as a part of the NuMachine Workstation The Macintosh Performa series was Apple Computer 's Consumer product family of Apple Macintosh Personal computers from 1992 until 1997 when the Processor Direct Slot or PDS, was a solution (actually a whole number of different solutions introduced by Apple Computer, in several of their Macintosh .

Later revisions of PCI added new features and performance improvements, including a 66 MHz 3. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. 3 V standard and 133 MHz PCI-X, and the adaptation of PCI signaling to other form factors. The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force. PCI-X ( Peripheral Component Interconnect Extended) is a Computer bus and Expansion card standard designed to supersede PCI. Both PCI-X 1. 0b and PCI-X 2. 0 are backward compatible with some PCI standards. With the introduction of the serial PCI Express standard in 2004, motherboard manufacturers have included progressively fewer PCI expansion slots in favor of the new standard. Not to be confused with PCI-X, a different bus architecture Peripheral Component Interconnect Express, officially abbreviated as PCI-E Although it is still common to see both interfaces implemented side-by-side, traditional PCI is likely to slowly die out in coming years.

Versions

Auto Configuration

PCI provides two separate 32-bit or 64-bit address spaces corresponding to the memory and I/O port address spaces of the x86 processor family. A motherboard is the central or primary Printed circuit board (PCB making up a complex electronic system such as a modern Computer or Laptop PCI-X ( Peripheral Component Interconnect Extended) is a Computer bus and Expansion card standard designed to supersede PCI. The range of Integer values that can be stored in 32 bits is 0 through 4294967295 or −2147483648 through 2147483647 using Two's complement encoding '64-bit' CPUs have existed in Supercomputers since the 1960s and in RISC -based workstations and servers since the early 1990s. In Computing, an address space defines a range of discrete addresses each of which may correspond to a physical or virtual Memory register, a network host See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal Addresses in these address spaces are assigned by software. A third address space, called the PCI Configuration Space, which uses a fixed addressing scheme, allows software to determine the amount of memory and I/O address space needed by each device. One of the major improvements Peripheral Component Interconnect (PCI had over other I/O architectures was its configuration mechanism Each device can request up to six areas of memory space or I/O port space via its configuration space registers. In Computing, input/output, or I/O, refers to the communication between an Information processing system (such as a Computer) and the outside

In a typical system, the firmware (or operating system) queries all PCI buses at startup time (via PCI Configuration Space) to find out what devices are present and what system resources (memory space, I/O space, interrupt lines, etc. In Computing, firmware is a computer program that is Embedded in a hardware device for example a Microcontroller. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination One of the major improvements Peripheral Component Interconnect (PCI had over other I/O architectures was its configuration mechanism ) each needs. It then allocates the resources and tells each device what its allocation is.

The PCI configuration space also contains a small amount of device type information, which helps an operating system choose device drivers for it, or at least to have a dialogue with a user about the system configuration.

Devices can have an optional ROM that can contain executable code for x86 or PA-RISC processors, an Open Firmware driver, or an EFI driver. See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal PA-RISC is a Microprocessor architecture developed by Hewlett-Packard 's Systems & VLSI Technology Operation. Open Firmware, or OpenBoot in Sun Microsystems parlance is a standard defining the interfaces of a computer Firmware system formerly endorsed by the The Extensible Firmware Interface ( EFI) is a specification that defines a software Interface between an Operating system and platform Firmware This is typically necessary for devices that may be used during system startup, before device drivers are loaded by the operating system.

Interrupts

Devices are required to follow a protocol so that the interrupt lines can be shared. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change The PCI bus includes four interrupt lines, all of which are available to each device. However, they are not wired in parallel as are the other traces. The positions of the interrupt lines rotate between slots, so what appears to one device as the INTA# line is INTB# to the next and INTC# to the next. Single-function devices always use their INTA# for interrupt signaling, so the device load is spread fairly evenly across the four available interrupt lines. This alleviates a common problem with sharing interrupts.

PCI bridges (between two PCI buses) map the four interrupt traces on each of their sides in varying ways. Some bridges use a fixed mapping, and in others it is configurable. In the general case, software cannot determine which interrupt line a device's INTA# pin is connected to across a bridge. The mapping of PCI interrupt lines onto system interrupt lines, through the PCI host bridge, is similarly implementation-dependent. The result is that it can be impossible to determine how a PCI device's interrupts will appear to software. Platform-specific BIOS code is meant to know this, and set a field in each device's configuration space indicating which IRQ it is connected to, but this process is not reliable.

PCI interrupt lines are level-triggered. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change This was chosen over edge-triggering in order to gain an advantage when servicing a shared interrupt line, and for robustness: edge triggered interrupts are easy to miss. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change

Later revisions of the PCI specification add support for message-signalled interrupts. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change In this system a device signals its need for service by performing a memory write, rather than by asserting a dedicated line. This alleviates the problem of scarcity of interrupt lines. Even if interrupt vectors are still shared, it does not suffer the sharing problems of level-triggered interrupts. It also resolves the routing problem, because the memory write is not unpredictably modified between device and host. Finally, because the message signaling is in-band, it resolves some synchronization problems that can occur with posted writes and out-of-band interrupt lines. See also Signalling (telecommunications In Telecommunications, in-band signaling is the sending of Metadata and control information in Out-of-band is a technical term with different uses in Communications and Telecommunication.

PCI Express does not have physical interrupt lines at all. Not to be confused with PCI-X, a different bus architecture Peripheral Component Interconnect Express, officially abbreviated as PCI-E It uses message-signalled interrupts exclusively.

Conventional hardware specifications

A typical 32-bit PCI card, in this case a SCSI adapter from Adaptec
A typical 32-bit PCI card, in this case a SCSI adapter from Adaptec
A PCI-X Gigabit Ethernet expansion card
A PCI-X Gigabit Ethernet expansion card

These specifications represent the most common version of PCI used in normal PCs. Adaptec is a Computer hardware company based in Milpitas California that primarily produces Host adapters for connecting storage devices Gigabit Ethernet (GbE or 1 GigE is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the

Variants

Conventional

Physical card dimensions

Full-size card

The original "full-size" PCI card is specified as a height of 107 mm (4. 2 inches) and a depth of 312 mm (12. Inches redirects here To see the Les Savy Fav album see Inches. 283 inches). The height includes the edge card connector. However, most modern PCI cards are half-length or smaller (see below) and many PCs cannot fit a full size card.

Backplate

In addition to these dimensions the physical size and location of a card's backplate are also standardized. The backplate is the part that fastens to the card cage to stabilize the card and also contains external connectors, so it usually attaches in a window so it is accessible from outside the computer case.

The card itself can be a smaller size, but the backplate must still be full-size and properly located so that the card fits in any standard PCI slot.

Half-length extension card (de-facto standard)

This is in fact the practical standard now - the majority of modern PCI cards fit inside this length.

Low-profile (half-height) card

The PCI organization has defined a standard for "low-profile" cards, which basically fit in the following ranges:

The bracket is also reduced in height, to a standard 3. 118 inches (79. 2 mm).

These cards may be known by other names such as "slim".

Mini PCI

This is a specialist version of PCI slot intended for laptops and the like.

Other physical variations

Typically consumers systems specify "N x PCI slots" without specifying actual dimensions of the space available. In some small form-factor systems, this may not be sufficient to allow even "half-length" PCI cards to fit. Despite this limitation, these systems are still useful because many modern PCI cards are considerably smaller than half-length.

Card keying

Typical PCI cards present either one or two key notches, depending on their signaling voltage. Cards requiring 3. 3 volts have a notch 56. 21mm from the front of the card (where the external connectors are) while those requiring 5 volts have a notch 104. 47mm from the front of the card. So called "Universal cards" have both key notches and can accept both types of signal.

See also

References

  1. ^ VLB was designed for 486-based systems, yet even the more generic PCI was to gain prominence on that platform. This is a list of device bandwidths: the Net bit rate (or more informally Digital bandwidth) of some computer devices employing methods of data transport is quantified The Advanced Microcontroller Bus Architecture was introduced in 1996 and is widely used as the on-chip bus for ARM processors Industry Standard Architecture (in practice almost always shortened to ISA) was a Computer bus standard for IBM compatible computers The Extended Industry Standard Architecture (in practice almost always shortened to EISA and frequently pronounced "eee-suh" is a bus standard for IBM compatible Micro Channel Architecture (in practice almost always shortened to MCA) was a proprietary 16- or 32-bit parallel Computer bus Mini PCI is a standard for a Computer bus for attaching peripheral devices to a Computer Motherboard and is an adaptation of NuBus is a 32-bit parallel Computer bus, originally developed at MIT as a part of the NuMachine Workstation Zorro II is the name of the general purpose expansion bus used by the Amiga 2000 computer Released as the expansion bus of the Commodore Amiga 3000 in 1990, the Zorro III Computer bus was used to attach peripheral devices The VESA Local Bus (usually abbreviated to VL-Bus or VLB) was mostly used in personal computers Not to be confused with PCI-X, a different bus architecture Peripheral Component Interconnect Express, officially abbreviated as PCI-E PCI-X ( Peripheral Component Interconnect Extended) is a Computer bus and Expansion card standard designed to supersede PCI. One of the major improvements Peripheral Component Interconnect (PCI had over other I/O architectures was its configuration mechanism

External links

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