Peripheral Component Interconnect

Peripheral Component Interconnect in English

Acronyms Technology

Abbreviated as PCI by Abbreviationfinder, Peripheral Component Interconnect is a standard computer bus for connecting peripheral devices directly to your motherboard. These devices can be integrated circuits fitted into it (so-called “planar devices” in the PCI specification) or expansion cards that fit into connectors. If it stops working, the USB-RJ45 Adapter can be used.


Work on PCIs began in the Intel laboratory in 1990 located in Atlacomulco, Mexico. PCI1.O which was only a component level specification was released on June 22, 1992. The PCI 2.O was the first to set the standard for the motherboard connector and spot, it was released in 1993. PCI 2.1 was released on June 1, 1995.
PCI was immediately put to use by servers, replacing MCA and EISA as an option to the expansion bus.

In PC it was slower to replace the VESA Local Bus and did not gain sufficient market penetration until after 1994 with the second generation of Pentiums. By 1996 VESA was phased out and companies replaced even 80486 computers. Apple adopted PCI for the Power Macintosh (replacing NuBus) in mid- 1995 and the Performa (replacing LC PDS) in mid- 1996.

New PCI versions added features and performance improvements including a 66MHz 3.3V standard and a 133MHz standard called PCI-X. Both PCI-X1.0b and PCI-X2.0 are compatible with their predecessors. With the introduction of the serial version PCI Express in 2004, motherboard manufacturers are including fewer and fewer PCI slots in favor of the new standard, although it is still common to see both interfaces implemented.

Auto Configuration

The PCI has 2 separate 32-bit and 64-bit address spaces corresponding to the memory and port I / O address of the X86 processor family. Addressing is assigned by the Software. A third address space called the PCI Configuration Space, which uses a corrected addressing scheme that allows the software to determine the amount of memory and input / output address space needed by each device. Each device you connect can request up to six memory space areas or I / O port spaces through its configuration space register.

In the typical system, the Firmware (or Operating System) consults all the PCI at startup (via PCI configuration space) to find out what devices are present and what resources and tells each device what its housing is. The PCI configuration space also contains a small amount of information about each device which helps the operating system to choose its drivers or at least have a dialog about the system configuration.

Devices can have a ROM that contains executable code for x86 or PA-RISC processors, an Open Firmware driver, or an EFI driver. These are typically necessary for devices used during system startup, before their drivers are loaded by the operating system.

They are also PCI Latency Timers that are a mechanism for the PCI Bus-mastering device to share the PCI bus more fairly. Where ‘fair’ in this case means that the devices did not use large portions of the available PCI bus bandwidth, that others are not able to get and are needed for the job. Note, this does not apply to PCIE.

The way this works is because each PCI device can operate in bus-master mode which is required to implement a clock, called a latency clock that limits the time that each device can occupy the PCI bus. When the counter reaches 0 the device is requested to leave the bus. If there is no other device waiting for ownership of the bus, you can simply get it back and transfer more data.

There is a PCI latency tool available. You can use a search engine for the latest version. This tool will be able to change / set the latency for any PCI.

Hardware specifications

Typical 32-bit PCI card. In this case, an Adaptec SCSI controller. These specifications represent the version of PCI most commonly used in PCs
• 33.33 MHz clock with synchronous transfers

  • 32-bit or 64-bit bus width
  • Maximum transfer rate of 133 MB per second on the 32-bit bus (33.33 MHz × 32 bits ÷ 8 bits / byte = 133 MB / s)
  • 266MB / s maximum transfer rate on 64-bit bus.
  • 32-bit address space (4 GB)
  • 32-bit I / O port space (currently deprecated)
  • 256 bytes of configuration space.
  • 3 V or 5 V, depending on the device
  • reflected-wave switching

Conventional PCI variants

  • Cardbus is a 32-bit, 33 MHz PCI PCMCIA format
  • Compact PCI, uses Eurocard size modules plugged into a PCI daughter board.
  • PCI 2.2 operates at 66 MHz (requires 3.3 volts on signals) (maximum transfer rate of 503 MiB / s (533MB / s).
  • PCI 2.3 allows the use of 3.3 volts and universal flag, but does not support 5 volts on the cards.
  • PCI 3.0 is the final official bus standard, with the 5-volt support completely removed.
  • PCI-X changes the protocol slightly and increases the data transfer rate to 133 MHz (maximum transfer rate of 1014 MiB / s).
  • PCI-X 2.0 specifies a ratio of 266 MHz (maximum transfer rate of 2035 MiB / s) and also 533 MHz, expands the configuration space to 4096 bytes, adds a 16-bit bus variant and uses signals of 1, 5 volts.
  • Mini PCI is a new format of PCI 2.2 for internal use in notebooks.
  • PC / 104-Plus is an industrial bus that uses PCI signals with different connectors.
  • Advanced Telecommunications Computing Architecture (ATCA or AdvancedTCA) is the next generation of buses for the telecommunications industry.
  • PXI is the extension of the PCI bus for instrumentation and control.

Full size card

The original “full-size” PCI card is about 107 mm (4.2 inches) thick and 312 mm (12.283 inches) long. Height includes card edge connector. However, most modern PCI cards are half-length or smaller (see below), and many personal computers cannot fit a full-size card.

The backplate card

In addition to these dimensions, the size of the Backplate is also standardized. The backplate is the metal piece on the edge that is used to secure it to the chassis and contains the external connectors. The card may be smaller in size, but the backplate must be full-size and properly localized. Regarding the previous ISA bus, it is located on the opposite side of the board to avoid errors.

The “half-length” extension card (de facto standard)

This is in fact the practical standard today – most modern PCI cards fit within these dimensions.
• Width: 0.6 inches (15.24 mm) • Depth: 6.9 inches (175.26 mm) • Height: 4.2 inches (106.68 mm)

The low profile card (medium height)

The PCI organization has defined a standard for “low profile” cards that is basically suitable in the following ranges:

  • Height: 1.42 inches (36.07 mm) to 2.536 inches (64.41 mm)
  • Depth: 4.721 inches (119.91 mm) to 6.6 inches (167.64 mm)

The shelf is also reduced in height to a standard 3.118 inches (79.2 mm). The smaller shelf does not fit a standard personal computer. Many manufacturers solve this by supplying both types of shelves (the shelves are typically bolted to the card so changing them is not difficult).

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

  • low profile PCI FAQ
  • low profile PCI Specification

Mini PCI

Mini PCI was added to version 2.2 PCI for use in notebook computers and uses a 32-bit, 33 MHz bus with boosted connections (3.3 V only) and support for the dominating bus and DMA. The standard size for Mini PCI cards is approximately 1/4 of their natural size counterparts. Since there is no external access to the card in the same way as there is for desktop PCI cards, Mini PCIs are generally limited in the functions that they can perform.

Many Mini PCI devices were developed with Wi-Fi Technology, Fast Ethernet, Bluetooth, Modems (often Winmodems), sound cards, Cryptographic accelerators, SCSI, IDE / ATA, SATA combination cards, and controllers. Regular PCI cards can be used with Mini PCI-equipped Hardware and vice versa, using Mini-PCI to PCI and PCI-to-Mini PCI converters. Mini PCI has been replaced by PCI Express Mini Card.

The Technical Details of Mini PCI Cards

Mini PCI cards have a maximum consumption of 2W, which also limits the functionality that can be implemented in this form factor. They require that they also support the CLKRUN # PCI, the signal used to start and stop the PCI clock for power management purposes.

There are three card form factors: Type I, Type II, and Type III. The card connector used for each type includes: Type I and II use a 100-pin drop connector, while Type III uses a 124-pin edge connector, eg. ex: the connector for Type I and II differ by this from Type III, where the connector is on the edge of a card, as with an SO-DIMM.

The additional 24 pins provide the required supplemental signals to the input / output path behind the connector system (audio, AC link, LAN, telephone line interface). Type II cards have RJ11 and RJ45 connectors mounted. These cards should be located at the edge of the computer or docking station so that the RJ11 and RJ45 ports can be mounted for external access.

Other physical variations

Typical consumer systems specify “N x PCI slots” without specifying the actual dimensions of the available space. In some small form factor systems, this is not yet sufficient for “half-length” PCI cards to fit in that slot. Despite this limitation, these systems are still useful because many modern PCI cards are considerably smaller than half-size ones.

Pulsation card

Typical PCI cards feature one or two key notches, depending on their rated voltage. Cards that require 3.3 volts have a 56.21mm notch on the front of the card (where the external connectors are), while those that require 5 volts have a 104.47mm notch on the front of the card. The so-called “Universal cards” have both key notches and can accept both types of signal.

Peripheral Component Interconnect