A bus in the scope of computer architecture is a subsystem that transfers data between computer components inside a computer or between a computer and another device. A bus that carries data within a computer is called internal bus. The most common internal bus today is PCI (Peripheral Component Interconnect,) bus. Similarly, a bus that carries data between two computers or between a computer and another device is call external bus. The most widely used external bus today is USB (Universal Serial Bus).
The form of data transfer in a computer buses can be in parallel, which data are carried in parallel on multiple wires, or in serial, which data are carried in bit-serial.
Examples of internal computer buses include
- Parallel buses: ASUS Media Bus proprietary, Computer Automated Measurement and Control (CAMAC), Extended ISA (EISA)
Industry Standard Architecture (ISA), Low Pin Count (LPC), MBus, MicroChannel (MCA), Multibus for industrial systems,
NuBus (IEEE 1196), OPTi local bus, Conventional PCI, Parallel ATA (aka Advanced Technology Attachment, ATA, PATA, IDE, EIDE, ATAPI, etc.) disk/tape peripheral attachment bus, Q-Bus, S-100 bus (IEEE 696), SBus (IEEE 1496), SS-50 Bus, STEbus, STD Bus (STD-80 and STD32), Unibus, VESA Local Bus (VLB, VL-bus), VMEbus.
- Serial buses: 1-Wire, HyperTransport, I²C, PCI Express (PCIe), Serial ATA (SATA), Serial Peripheral Interface Bus (SPI bus), UNI/O, SMBus.
Examples of external computer buses include
- Parallel buses: HIPPI HIgh Performance Parallel Interface, IEEE-488 (GPIB, General-Purpose Interface Bus, and HPIB, Hewlett-Packard Instrumentation Bus), PC card (PCMCIA).
- Serial buses: USB (Universal Serial Bus), EIA-485, eSATA (external serial ATA), FireWire (IEEE 1394).