The components inside your computer talk to each other in various different ways. Most of the internal system components, including the processor, cache, memory, expansion cards and storage devices, talk to each other over one or more "buses".
A bus, in computer terms, is simply a channel over which information flows between two or more devices (technically, a bus with only two devices on it is considered by some a "port" instead of a bus). A bus normally has access points, or places into which a device can tap to become part of the bus, and devices on the bus can send to, and receive information from, other devices. The bus concept is rather common, both inside the PC and outside in the real world as well. In fact, your home telephone wiring is a bus: information flows through the wiring that goes through your house, and you can tap into the "bus" by installing a phone jack, plugging in the phone and picking it up. All the phones can share the "information" (voice) on the bus.
Modern Pentium class motherboards have a data bus with 64 bits. That is the width of the data highway that goes in and out of the processor. The Pentium processors, however, do use 32-bit registers to handle 32-bit instructions.
Bus speeds and widths have increased due to faster processors and the needs of multimedia applications.
- Typical bus names and widths are:
- Industry Standard Architecture (ISA) - 8 or 16 bits
- Extended Industry Standard Architecture (EISA) - 8 or16 bits
- Microchannel Architecture (MCA) - 16 or 32 bits
- VESA Local Bus (VLB) - 32 bits
- Peripheral Component Interconnect (PCI) - 32 or 64 bits
- Accelerated Graphics Port (AGP ) - 32 bits