computer architecture In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, t ...

, a local bus is a

computer bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ex ...

that connects directly, or almost directly, from the

central processing unit A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...

(CPU) to one or more slots on the

expansion bus In computing, an expansion card (also called an expansion board, adapter card, peripheral card or accessory card) is a printed circuit board that can be inserted into an electrical connector, or expansion slot (also referred to as a bus slo ...

. The significance of direct connection to the CPU is avoiding the

bottleneck Bottleneck literally refers to the narrowed portion (neck) of a bottle near its opening, which limit the rate of outflow, and may describe any object of a similar shape. The literal neck of a bottle was originally used to play what is now known as ...

created by the expansion bus, thus providing fast

throughput Network throughput (or just throughput, when in context) refers to the rate of message delivery over a communication channel, such as Ethernet or packet radio, in a communication network. The data that these messages contain may be delivered ov ...

. There are several local buses built into various types of computers to increase the speed of data transfer (i.e.

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

). Local buses for expanded memory and video boards are the most common.

VESA Local Bus The VESA Local Bus (usually abbreviated to VL-Bus or VLB) is a short-lived expansion bus introduced during the i486 generation of x86 IBM-compatible personal computers. Created by VESA (Video Electronics Standards Association), the VESA Local Bus ...

and

Processor Direct Slot A processor direct slot (PDS) is a slot incorporated into many older Macintosh models that allowed direct access to the signal pins of a CPU, similar to the functionality of a local bus in PCs. This would result in much higher speeds than having ...

were examples of a local bus design. Although VL-Bus was later succeeded by AGP, it is not correct to categorize AGP as a local bus. Whereas VL-Bus operated on the CPU's

memory bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ex ...

at the CPU's clock speed, an AGP peripheral runs at specified clock speeds that run independently of the CPU clock (usually using a divider of the CPU clock).

References

Computer buses {{Compu-hardware-stub

See also

References