What Is Peripheral Component Interconnect (PCI)?

PCI bus connects peripherals to the motherboard

Peripheral Component Interconnect is a common connection interface for attaching computer peripherals to the motherboard. PCI was popular between 1995 and 2005 and was most often used to connect sound cards, network cards, and video cards.

PCI is also an abbreviation for other unrelated technical terms, like protocol capability indicator, program-controlled interrupt, panel call indicator, personal computer interface, and more.

Firewire Card for PC and Firewire Cables

Is PCI Still Used Today?

Modern computers mainly use other interface technologies like USB or PCI Express (PCIe). Some desktop computers might have PCI slots on the motherboard to maintain backward compatibility. However, the devices that were attached as PCI expansion cards are now either integrated onto motherboards or attached by other connectors like PCIe.

Other Names for PCI

A PCI unit is called a PCI bus. A bus is a term for a path between the components of a computer. You might also see this term described as conventional PCI. However, don't confuse PCI with PCI compliance, which means payment card industry compliance, or PCI DSS, which means payment card industry data security standard.

How Does PCI Work?

A PCI bus lets you change different peripherals that are attached to the computer system. Usually, there are three or four PCI slots on a motherboard. With PCI, you can unplug the component you want to swap and plug in the new one in the PCI slot. If you have an open slot, you can add another peripheral like a second hard drive.

Computers might have more than one type of bus to handle different traffic types. The PCI bus used to come in both 32-bit and 64-bit versions. PCI runs at 33 MHz or 66 MHz.

PCI Cards

PCI cards come in several shapes and sizes, also known as form factors. Full-size PCI cards are 312 millimeters long. Short cards range from 119 to 167 millimeters and fit into smaller slots. There are other variations, such as compact PCI, Mini PCI, Low-Profile PCI, and others.

PCI cards use 47 pins to connect, and PCI supports devices that use 5 volts or 3.3 volts. 

Peripheral Component Interconnect History

Intel developed the PCI bus in the early 1990s. It provided direct access to system memory for connected devices through a bridge connecting to the front-side bus and eventually to the CPU. PCI 1.0 was released in 1992, PCI 2.0 in 1993, PCI 2.1 in 1995, PCI 2.2 in 1998, PCI 2.3 in 2002, and PCI 3.0 in 2004.

PCI became popular when Windows 95 introduced its Plug and Play (PnP) feature in 1995. Intel had incorporated the PnP standard into PCI, which gave it an advantage over ISA. PCI didn't require jumpers or dip switches, as ISA did.

PCIe improved on PCI and has a higher maximum system bus throughput, a lower I/O pin count, and is smaller physically. It was developed by Intel and the Arapaho Work Group. It became the primary motherboard-level interconnect for PCs by 2012 and replaced Accelerated Graphics Port as the default interface for graphics cards for new systems.

PCI-X is a similar technology to PCI. Standing for Peripheral Component Interconnect eXtended, PCI-X improves bandwidth on the 32-bit PCI bus for servers and workstations.

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