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Building & Buying a PC

Volume I, Issue No.3 June 21, 1995

http://www.buildorbuy.org/pdf/b&b003pc.pdf

ALL ABOARD! THE COMPUTER BUS-

Common pathway between hardware devices. A computer bus connectsthe CPU to its main memory and the memory banks that reside onthe control units of the peripheral devices. It is made up oftwo parts. Addresses are sent over the address bus to signal amemory location, and the data is transferred over the data busto that location. Widely-used computer buses are ISA, EISA, NuBus,Micro Channel, TURBOchannel, VMEbus, MULTIBUS and STD bus. Ourcurrent bus, the (VLB) Vesa Local Bus is history. The Bus of choiceisthe PCI bus by Intel.

Why Is It Called a Bus?

The term was coined after a real bus, because all bus stops areavailable to everyone on a bus. The same goes for an electronicbus. All signals on the bus are available to all stations or devicesconnected to it.

Bus Card

Expansion board (card) that plugs into the computer's expansionbus.

Bus Mastering

Bus design that allows add-in boards to process independentlyof the CPU and to be able to access the computer's memory andperipherals on their own.

Bus Mouse

Mouse that plugs into an expansion board. It takes up an expansionslot whereas a serial mouse takes up a serial port. The choicedepends on how many devices must be connected to each type ofsocket.

RAM

(Random Access Memory) Computer's primary

workspace. Also true of most memory chips (ROMs, PROMs, etc.),"random" means that the contents of each byte can bedirectly accessed without regard to the bytes before or afterit. RAM chips require power to maintain their content. Seedynamic RAM, static RAM and memory.

Dynamic RAM

Most common type of computer memory, called DRAM. It usually usesone transistor and a capacitor to represent a bit. The capacitorsmust be energized hundreds of times per second in order to maintainthe charges. Unlike firmware chips (ROMs, PROMs, etc.) both majorvarieties of RAM (dynamic and static) lose their content whenthe power is turned off.

In memory advertising, dynamic RAM is often stated as a packagetype; for example, "DRAMs, SIMMs and SIPs on sale."It should be "DIPs, SIMMs and SIPs," as all three packagestypically hold dynamic RAM chips.

Definitions from the Electronic Computer Glossary @ 215-297-5999,cost $29.95.

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