PC data buses

PC data buses

The bus in a PC is the common interface between the CPU and peripheral devices. Parallel buses use multiple lines for data (eight lines for 8-bit buses; 16 lines for 16-bit and so on). Serial buses use one line for data. Following are the various buses used in the PC.

Parallel Buses (Current)

PCI - For a Variety of Peripherals
The PCI bus, available in 32- and 64-bit versions, is the most popular bus architecture in PCs as well as numerous other platforms. In 2002, PCI Express was introduced, providing greatly enhanced speeds, especially for the display system. See PCI and PCI Express.

IDE/ATA - For Drives
For decades, IDE has been a widely used interface for hard disks and CD/DVD drives. See IDE.

Serial Buses (Current)

SATA - For Drives
SATA is a faster version of IDE and uses a thinner cable. See SATA.

USB - For External Connections
USB is used to permanently or temporarily attach myriad devices, including hard disks, printers, cameras and smartphones. See USB.

FireWire - For Video
FireWire has been mostly used for digital camera connections. See FireWire.

Parallel Buses (Earlier)

AGP - For the Display Adapter
AGP was designed for faster screen display. Motherboards with AGP have one slot for only the display adapter. See AGP and display adapter.

ISA - An Early PC Bus
Pronounced "eye-suh," it evolved from the first PC bus in 1981 and originated on IBM's PC AT in 1984. See ISA.

Micro Channel - IBM's Bus
IBM introduced the 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 - Faster than ISA
Pronounced "ee-suh," this was an extension of ISA created by major vendors to counter IBM's Micro Channel. EISA slots accepted both EISA and ISA cards. EISA was used in servers but later abandoned for PCI. See EISA.

VL-bus - Faster than ISA
The 32-bit VL-bus was introduced during the 486 era and offered higher speed than ISA. It then gave way to PCI. See VL-bus.

Types of Expansion Boards

Of the six parallel bus types in this illustration, all have disappeared from new systems with the exception of PCI.