*********************************************************************
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.
*********************************************************************

                        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)