Bus (computing)

A computer bus is an electrical bus that transfers data or power between computer components inside a computer or between computers.

Busses can be parallel busses, which carry data words striped across multiple wires, or serial busses, which carry data in bit-serial form. The addition of extra power and control connections, differential drivers, and data connections in each direction usually means that most serial busses have more conductors than the minimum of two used in the I²C serial bus.

Busses can also be wired in a multidrop or daisy-chain electrical topology.

Most computers have both internal and external buses. An 'internal bus' connects all the internal components of a computer to the motherboard (and thus, the CPU and Main Memory). An 'external bus' connects external peripherals to the motherboard.

Network connections such as Ethernet are not generally regarded as buses, although the difference is largely conceptual rather than practical.

Examples of Internal Computer Buses

• Peripheral Component Interconnect or PCI
• Industry Standard Architecture or ISA
• Extended ISA or EISA
• EuroCard
• Versabus Module Eurocard or VME
• NuBus or IEEE 1196
• Advanced Technology Attachment or ATA (aka IDE, EIDE, ATAPI, etc.)
• VESA Local Bus or VLB or VL-bus
• I²C (also used in other standards such as VESA DDC and the Intelligent Platform Management Interface)

Examples of External Computer Buses

• ACCESS.bus (aka A.b)
• Apple Desktop Bus (ADB)
• Universal Serial Bus or USB
• Firewire or IEEE 1394
• Small Computer Systems Interface or SCSI
• General-Purpose Instrumentation Bus or GPIB