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How CPUs are Made (Page 1/5)


Posted: November 22, 2000
Written by: Tuan "Solace" Nguyen
Parts of this article, including diagrams were reprinted with permission from Intel.com.

Introduction

Itís that time of the week again, when Iím just itching to find out how something works. It just bothers me when I donít know how something functions, especially when I use that thing everyday of my life. Iím talking about a processor, a CPU, a chip. How exactly is it made? Of course I already know how, thatís why Iím writing this guide, but perhaps you donít. Letís get on with the show.

Potato Chips

Every component inside your computer has some type of IC (integrated circuit) chip on it. And each chip is made with the same design principles in mind. These chips contain a small silicon die inside them, which contain thousands to millions of transistors.

Transistors

What is a transistor? Transistors are miniature electronic switches. They are the building blocks of a microprocessor, which is the brain of the computer. You can think of a transistor like it was a light switch. They have two operating positions, on and off. This on and off, or binary functionality of transistors enables the processing of information in a computer. This is why binary numbers are based on 1ís (on) and 0ís (off).



At their most basic level, transistors may seem simple. But their development actually required many years of painstaking research. Before transistors, computers relied on slow, inefficient vacuum tubes and mechanical switches to process information. In 1958, engineers (one of them being Intel founder Robert Noyce) managed to put two transistors onto a silicon crystal and create the first integrated circuit, that led to the microprocessor.

The only information computers understand are electrical signals that are switched on and off. To comprehend transistors, it is necessary to have an understanding of how a switched electronic circuit works.

Switched electronic circuits consist of several parts. One is the circuit pathway where the electrical current flows - typically through a wire. Another is the switch, a device that starts and stops the flow of electrical current by either completing or breaking the circuit's pathway. If you cut a wire, the flow will stop, and if you reconnect the ends, the flow continues. So in essence, you can be a human transistor.

Transistors have no moving parts and are turned on and off only by electrical signals. The on/off switching of transistors facilitates the work performed by microprocessors. Something that has only two states (on or off), like a transistor, can be referred to as binary. The transistor's on state is represented by a 1 and the off state is represented by a 0. Specific sequences and patterns of 1s and 0s generated by multiple transistors can represent letters, numbers, colors and graphics. This is known as binary notation.



For example, 1 in decimal would be 1 in binary. 2 would be 10. 3 would be 11. 4 would be 100. 5 would be 101. 6 would be 110. 7 would be 111. And so on. Hereís ďTweak3DĒ written in binary:

T 0101 0100
W 0101 0111
E 0100 0101
A 0100 0001
K 0100 1011
3 0000 0011
D 0100 0100

Letters are represented by ASCII in this example. E.g. "T" is the ASCII equivalent of 01010100 (binary), or 84 (decimal). Interesting, huh? Maybe I should type out this entire article in binary. What fun! So how exactly does a transistor work inside a processor? Letís take a look.

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