Topics: Microprocessor, Central processing unit, Computer Pages: 8 (3564 words) Published: February 12, 2015
Howstuffworks.com's "How Microprocessors Work"

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How Microprocessors Work
by Marshall Brain

The computer you are using to read this page uses a microprocessor to do its work. The microprocessor is the heart of any normal computer, whether it is a desktop machine, a server, or a laptop. The microprocessor you are using might be a Pentium, a K6, a PowerPC, a Sparc or any of the many other brands and types of microprocessors, but they all do approximately the same thing in approximately the same way.

If you have ever wondered what the microprocessor in your computer is doing, or if you have ever wondered about the differences between different microprocessors, then this edition of How Stuff Works will be incredibly interesting. You will learn how fairly simple digital logic techniques allow a computer to do its job, whether its playing a game or spell checking a document!

Microprocessor History
A microprocessor - also known as a CPU or Central Processing Unit - is a complete computation engine that is fabricated on a single chip. The first microprocessor was the Intel 4004, introduced in 1971. The 4004 was not very powerful - all it could do was add and subtract, and it could only do that four bits at a time. But it was amazing that everything was on one chip. Prior to the 4004, engineers built computers either from collections of chips or from discrete components (transistors wired one at a time). The 4004 powered one of the first portable electronic calculators.

The first microprocessor to make it into a home computer was the Intel 8080, a complete 8-bit computer on one chip introduced in 1974. The first microprocessor to make a real splash in the market was the Intel 8088, introduced in 1979 and incorporated into the IBM PC (which first appeared in 1982 or so). If you are familiar with the PC market and its history, you know that the PC market moved from the 8088 to the 80286 to the 80386 to the 80486 to the Pentium to the Pentium-II to the new Pentium-III. All of these microprocessors are made by Intel and all of them are improvements on the basic design of the 8088. The new Pentiums-IIIs can execute any piece of code that ran on the original 8088, but the Pentium-III runs about 3,000 times faster!

The following table helps you to understand the differences between the different processors that Intel has introduced over the years.

Date Transistors Microns Clock speed Data width MIPS


1974 6,000


2 MHz


0.64 MIPS

First home computers


1979 29,000


5 MHz

16 bits, 8
bit bus

0.33 MIPS

First IBM PC


1982 134,000


6 MHz

16 bits


IBM ATs. Up to 2.66
MIPS at 12 MHz

http://www.howthingswork.com/microprocessor.htm?printable=1 (1 of 8) [28.1.2001 17:13:27]

Howstuffworks.com's "How Microprocessors Work"


1985 275,000



16 MHz

32 bits


1989 1,200,000 1

25 MHz

32 bits


1993 3,100,000 0.8

60 MHz

Pentium II 1997 7,500,000 0.35

233 MHz

Pentium III 1999 9,500,000 0.25

450 MHz

32 bits, 64
bit bus
32 bits, 64
bit bus
32 bits, 64
bit bus

Eventually 33 MHz,
11.4 MIPS
Eventually 50 MHz,

100 MIPS

Eventually 200 MHz

400 MIPS?

Eventually 450 MHz,
800 MIPS?

1,000 MIPS?

Compiled from The Intel Microprocessor Quick Reference Guide

Information about this table:
What is a Chip?
● The date is the year that the processor
was first introduced. Many processors
A chip is also called an integrated circuit.
are re-introduced at higher clock speeds Generally it is a small, thin piece of silicon onto for many years after the original release which the transistors making up the date.
microprocessor have...
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