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Definition: PC data buses

The bus in a PC is the common hardware interface between the CPU and peripheral devices. Parallel buses use multiple lines (wires) for data. Serial buses use one line for data. Following are the various buses used in the PC.


PCI Express - (Parallel in Serial Form)
PCI Express (PCIe) is the current bus interface, superseding PCI. New PC motherboards generally have only PCIe slots. See PCI Express.

PCI - (Parallel)
PCI was very popular in PCs, Macs and other hardware platforms. Superseded by PCI Express (PCIe), motherboards may be available with one PCI slot. See PCI.

USB - (Serial)
USB is used extensively to permanently or temporarily attach myriad devices, including drives, printers, cameras and flash drives. See USB.


FireWire - (Serial)
FireWire was mostly used for digital camera connections. Popularized by Apple, adapters were required to use FireWire on new Macs. See FireWire.

AGP - (Parallel)
The AGP was designed for faster screen display, and one slot was found on motherboards. AGP was superseded by PCI Express. See AGP and display adapter.

ISA - (Parallel)
Pronounced "eye-suh," ISA evolved from the first PC bus in 1981 and originated on IBM's PC AT in 1984. See ISA.

Micro Channel - (Parallel)
IBM introduced Micro Channel with its PS/2 line in 1987, then later supported ISA and eventually gave up Micro Channel for PCI. See Micro Channel.

EISA - (Parallel)
Pronounced "ee-suh," this extension of ISA was created to counter Micro Channel. EISA slots also accepted ISA cards. EISA was used in servers but later abandoned for PCI. See EISA.

VL-bus - (Parallel)
The VL-bus was introduced during the 486 era and offered more speed than ISA. It too gave way to PCI. See VL-bus.

Types of Expansion Cards
Except for PCI Express and PCI, all the rest of these interfaces have been discontinued.