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A Peripheral Component Interconnect Bus (PCI bus) connects the CPU and expansion boards such as modem cards, network cards and sound cards. These expansion boards are normally plugged into expansion slots on the motherboard.
The PCI local bus is the general standard for a PC expansion bus, having replaced the Video Electronics Standards Association (VESA) local bus and the Industry Standard Architecture (ISA) bus. PCI has largely been replaced by USB.
This term is also known as conventional PCI or simply PCI.
PCI requirements include:
PCI specifications are standardized by the Peripheral Component Interconnect Special Interest Group.
Today, most PCs do not have expansion cards, but rather devices integrated into the motherboard. The PCI bus is still used for specific cards. However, for practical purposes, USB has replaced the PCI expansion card.
During system startup the operating system searches for all PCI buses to attain information about the resources needed for each device. The OS communicates with each device and assigns system resources, including memory, interrupt requests and allotted input/output (I/O) space.