What Is a PCI Bridge Device?

By Michael Logan

A motherboard with card slots for various add-on devices.
i motherboard image by Falk from Fotolia.com

The open architecture of personal computers allows manufacturers to build add-on cards, such as modems, video cards, USB ports and network devices. These cards plug directly into card slots on the motherboard. The hardware connection between the card slots and the microprocessor is called a bridge.


PCI is an acronym for Peripheral Component Interconnect. PCI devices may be integrated directly on the motherboard or function as an expansion board that plugs into a card slot on the motherboard.


A PCI bridge is a hardware connection between two different buses. The bridge may be PCI to PCI, PCI to ISA or some other kind of bus. Bus standards are limited by electrical characteristics. Adding devices called bridges allows the buses to be expanded. A PCI bridge allows expansion of the PCI bus by adding more buses to the system.

Device Drivers

PCI device drivers are programs designed to operate PCI devices located on the PCI bus. Each specific card or device on the PCI bus requires its own driver software.

Open Architecture

Third-party expansion boards that operate with their own device drivers allow manufacturers to build expansion cards without knowing the specific configuration of a specific motherboard. The manufacturer builds the device to conform to the PCI standard and codes a device driver to run it. The operating system integrates the device into the system.