PC data buses

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PC data buses

The bus in a PC is the common hardware 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 Express - Variety of Peripherals
PCI Express (PCIe) provides greatly enhanced speeds, especially for the display system. It provides parallel transfer in separate serial channels. New PC motherboards generally have only PCIe slots. See PCI Express.

PCI - Variety of Peripherals
The PCI bus has been the most popular bus architecture in PCs as well as in the Mac and other platforms. Superseded by PCI Express (PCIe), most new PC motherboards do not have PCI slots; however, millions of computers in use today are PCI based. See PCI.

Serial Buses (Current)

SATA - Drives
SATA is a faster version of the IDE architecture and uses a thinner cable. It is the mainstream interface for connecting internal hard disks, optical disks and SSDs; however, external connections are also available. See SATA.

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

FireWire - Video
FireWire has been mostly used for digital camera connections. Popularized by Apple, adapters are required to use FireWire on new Macs. See FireWire.

Parallel Buses (Earlier)

IDE/ATA - Drives
For decades, IDE was widely used for hard disks and CD/DVD drives, and IDE drives are still found on many PCs. However, new motherboards no longer have IDE slots. See IDE.

AGP - Graphics Card (Display Adapter)
AGP was designed for faster screen display. Motherboards with AGP had one slot for the display adapter. See AGP and display adapter.

ISA - First Mainstream 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 extension of ISA was created by major vendors to counter IBM's Micro Channel. EISA slots also accepted ISA cards. EISA was used in servers but later abandoned for PCI. See EISA.

VL-bus - Faster than ISA
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.