ZALMAN AMD Athlon/ Duron/Athlon XP Socket 462 CPU Manual de usuario descargar pdf (Pagina 6)

104 MIKE MEYERS’ A+ CERTIFICATION PASSPORT

Passport / Mike Meyers‘ A+ Certification Passport / Meyers / 226308-3 / Chapter 5

Address Space

The number of wires on the address bus defines the maximum amount of RAM

a CPU can theoretically address. This is called the address space. With a 32-bit

address bus, for example, the maximum amount of memory the CPU can

address is 2

, or 4,294,967,296 bytes (4 GB).

Concepts

Techs use certain concepts and terms to differentiate among CPUs, so you can

judge pretty quickly which specific make and model fits your client’s needs.

Specifically, the pipeline, clock speed, and clock multipliers give you a good

indication of the caliber of the CPU.

Pipeline

The term pipeline refers to the discrete series of steps that the CPU follows to

process commands. Think of a pipeline in terms of doing laundry. Doing laun-

dry follows an ordered series of steps: sort, wash, dry, iron, and fold or hang up.

Early, pre-Pentium CPUs had only a single pipeline and thus could process only

a single command at a time. With a complex mathematical command, for ex-

ample, the FPU might be working hard and the ALU sitting idle. The Pentium

introduced dual pipelines that enabled the CPU to process two commands si-

multaneously. Current CPUs have many more pipelines and can thus process

more commands at once.

Clock Speed

The CPU clock speed tells you how many calculation cycles a CPU can (in the

ory) execute per second. One calculation cycle per second is equal to 1 hertz

(Hz). Of course, nobody measures clock cycles in hertz, but rather in millions of

calculation cycles per second, or megahertz (MHz). These days, it’s more com

mon to see clock speed measured in billions of cycles per second, or gigahertz

(GHz).

Two things determine clock speed: the maximum speed of the CPU itself and

the maximum speed that the motherboard can handle. The CPU speed is deter

mined by the manufacturer and is set at the factory. The system crystal—a

quartz crystal circuit that oscillates at a fixed frequency when fed current—sets

the motherboard’s clock speed.

Multipliers

Early CPUs took the beat set by the clock and simply doubled it, thus enabling

the CPU to run internally at twice the speed of the motherboard. Modern CPUs

multiply the signal many times. A CPU running at 2 GHz on a 200-MHz system

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