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Last modified: Friday, January 18, 2002 

(1) A collection of wires through which data is transmitted from one part of a computer to another. You can think of a bus as a highway on which data travels within a computer. When used in reference to personal computers, the term bus usually refers to internal bus. This is a bus that connects all the internal computer components to the CPU and main memory. There's also an expansion bus that enables expansion boards to access the CPU and memory.

All buses consist of two parts -- an address bus and a data bus. The data bus transfers actual data whereas the address bus transfers information about where the data should go.

The size of a bus, known as its width, is important because it determines how much data can be transmitted at one time. For example, a 16-bit bus can transmit 16 bits of data, whereas a 32-bit bus can transmit 32 bits of data.

Every bus has a clock speed measured in MHz. A fast bus allows data to be transferred faster, which makes applications run faster. On PCs, the old ISA bus is being replaced by faster buses such as PCI.

Nearly all PCs made today include a local bus for data that requires especially fast transfer speeds, such as video data. The local bus is a high-speed pathway that connects directly to the processor.

Several different types of buses are used on Apple Macintosh computers. Older Macs use a bus called NuBus, but newer ones use PCI.

(2) In networking, a bus is a central cable that connects all devices on a local-area network (LAN). It is also called the backbone.

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For pages about bus . Also check out the following links!

Related Links

Microprocessor Comparison Chart 
A cut-to-the-chase guide that compares and contrasts popular processing chips.

PC system bus reference guide 
A complete look at the PC's system I/O buses. Includes coverage of the various functions and features of the bus, a look at ISA, VLB and PCI buses, plus older technologies, and the new AGP port.

Bit 3 Computer Corporation home page
Bit 3 Computer specializes in bus connection and bus extensions. Here, you can find links to their bus-to-bus adapter, expansion unit and bus repeater products.

Descriptions of bus standards
This PC Basics page, from Intel, provides an introduction to the four of the current microcomputer buses (ISA, EISA, VL/VESA and PCI).

Microsoft Bus and BIOS Design for PC Hardware
Contains links to technical information about BIOS and bus class design issues.

Microsoft Bus Specifications Page
Provides access to Microsoft and industry specifications for buses, including PCI, USB, and IEEE 1394 specifications and standards

Overview of PC Bus terms
Provides concise descriptions of bus, I/O bus, and the different kinds of expansion cards.

PC motherboard and system device reference
Comprehensive motherboard reference, covering all the major motherboard components. Looks at the physical motherboard, chipset, system buses, system cache, system resources, and the system BIOS.

The Online Journal of ISA Bus Controlled Systems
This online journal contains technical information, a list of ISA information databases, articles and trade show information, and other resources related to the ISA bus.

The Universal Serial Bus FAQ
Provides a comprehensive list of answers and questions to various aspects of universal serial bus technology.

Troubleshooting the Motherboard and System Devices
Focuses on problems related to the motherboard and system devices, including the components of the motherboard, along with system devices such as the cache and I/O buses, the BIOS and CMOS memory, system resources, and features such as Plug and Play. This page is from "The PC Guide."

Yahoo!'s buses page
Yahoo!'s directory of buses.

Yahoo!'s universal serial bus page
Yahoo!'s directory of universal serial bus.

related categories


related terms




address bus

AT bus


backside bus

bus mastering


clock speed


control bus




expansion bus

Fibre Channel

frontside bus


Industry Standard Architecture (ISA) bus

local bus



oscillator clock


system bus



VME bus


ZV Port

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