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- This article is being presented through the *StarBoard* Journal of
- the FlagShip/StarShip, SIGS (Special Interest Groups) on the
- Delphi and GEnie telecommunications networks. Permission is
- hereby granted to non-profit organizations only to reprint this
- article or pass it along electronically as long as proper credit
- is given to both the authors and the *StarBoard* Journal.
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-
- Sand, Wire, and Lights
- - or -
- What Makes Your Computer Tick!
- by
- Mike Stephens
- and
- Gary Funk
-
- By now, most of you know that your computer has a bunch of
- electronic chips in it. But, do you really know what goes on inside
- those little black packages? A chip is simply a very thin wafer of
- silicon (sand, if you prefer) that has been etched into a circuit
- pattern. Chips contain thousands of transistors and resistors. The
- 6510, the heart of the 64, is made of a type of transistor called
- MESFETS. These transistors are mostly used in digital logic circuits
- (such as digital watches and calculators). Transistors are made of two
- types of 'doped' silicon. Doped means it has been bombarded with other
- particles to give it either a positive or negative characteristic. To
- make a piece of silicon negative, it is usually doped with Boron gas at
- high temperatures. When these areas of positive and negative are placed
- together in certain patterns, they take on certain characteristics.
- They can be made to act as a switch, a variable resistor (JFETS), or as
- logic circuits.
-
- Thousands of these transistors are placed on a thin silicon wafer
- (about 1 cm by 1 cm). This is accomplished by using a photolithographic
- process and ultraviolet light to eat away certain areas of the wafer,
- creating a circuit pattern. Wires are attached to the wafer by either
- soldering or heating the silicon and melting the wire into it. The
- whole package is then put into a plastic case, called the Dual in-line
- Package, or DIP. This is your chip.
-
- The process sounds simple, but consider that the distances you are
- dealing with (such as distance between the connections in the circuit
- diagrams on the wafer) are only a few atoms wide. That is why they can
- fit so much onto a chip these days. That is also why specialized chips
- are so very expensive. Even with today's technology, it is almost
- impossible to make two chips exactly alike, but the differences are so
- subtle that your computer couldn't care less.
-
- If you remember several months ago NASA had to abort a Shuttle
- launch. The engines had fired, but the main computer shut them down.
- The reason for the abort? During the manufacture of the chips used to
- build the main computers, spattle found its way into the wafer. At the
- time of the launch, the spattle took that exact moment to short some of
- the transistors in the wafer. The computer, which is constantly
- checking its own circuits, as well as those on the shuttle, shut down
- the flight.
-
- The cost for the abort: $10 million for the shuttle preparations
- and men power, and $50,000 or so for a new computer chip. I told you
- specialized chips don't come cheap.
-
- So, next time you look inside your computer and see those big,
- black, beautiful DIPs, remember that many, many things are going on
- inside them. They are very delicate devices. Never remove a chip from a
- socket without a chip-remover; you can easily break the pins. Try not
- to ever touch the pins with your fingers or with any other object that
- may contain static electricity. Static charges can cook memory chips
- just as fast as sending ten million volts through them (perhaps, a
- little exaggeration but the point still stands). Also, don't think that
- every chip is the same. Don't replace what you think might be a
- defective chip with another (unless the numbers are the same)--take it
- to qualified, trained people. You won't regret it.
- ---------------------------------------------------------------------
- Gary Wayne = GWAYNE (GEnie FlagShip)
- GARYWAYNE (DELPHI FlagShip)