MICROPROCESSORS

Microprocessors, or CPU (Central Processing Unit) chips, are a relativly new invention; the first one being introduced by Intel in 1971. The one that probably started the personal computer revolution was Intel's 8080, produced in the early 70's, used in the first personal computer - the Altair 8800. (As a side-note, Microsoft was formed about this time and their first product was MicroSoft Basic for the Altair.)

The first microprocessor success story was the Z-80 (made by Zilog), a rip-off of Intel's 8080 chip, which was introduced in late 1975. It was the microprocessor used in some of the earliest home computers - such as the Radio Shack TRS-80 Model 1, and by pioneers Osborne and Kaypro.

In 1976 several former Motorola engineers (who had formed a company called MOS Technologies) released the 6502 which Steve Wozniak chose to design into the Apple I and Apple II computers. It was also used by several other companies in their first PCs and game machines - notably Commodore and Nintendo. The Motorola generated line of microprocessors are still powering Apple products.

The Intel generated line of microprocessors was chosen by IBM as the heart of their blockbuster Personal Computer, released in 1983. The Intel 8088 micro-processor, used in the IBM-PC, contained about 30,000 transistors and ran at a speed of just under 5 MegaHertz. By contrast, Intel's latest microprocessors contain nearly 30 million transistors and run in speeds in excess of 500 MegaHertz and 1 GigaHertz chips have already been produced.

To maybe make things a little clearer:

     a Hertz is a cycle per second,
     Mega means million
     (and Giga means billion).

So -
a microprocessor that runs at 5 Megahertz (5 MHz) can perform an action 5 million times per second -
     one that runs at 1 GigaHertz can perform that action 1,000 million times each second.

Speed is not the only measurement of a microprocessor. How many bits of data it can perform that action on at the same instant is also a factor. Microprocessors can only do a limited number of things - very rapidly, it's true, but still a limited number. They can perform one out of this limited set of actions on whatever quantity of bits is on the data bus. (DATA BUS - kind of like the highway where information comes and goes from the microprocessor). The microprocessor used in the IBM PC had an 8 bit data bus which means that it could work with 8 bits at a time. The next generation computer, the IBM PC-AT, used an Intel 80286 micro- processor which handled 16 bits at a time and the mainboards that used it were designed with a 16 bit data bus. The '386 computers that followed made the transition to a 32 bit machine, all '486 machines were 32 bit machines and the Pentium processors of today are all 64 bit machines. So, not only are modern microprocessors up to 200 times faster than the first PCs, they also handle 8 times as much data at the same time. And both of those numbers increase all the time - that's the nature of progress.

I'd like to throw in a word of caution here: all this information is relatively accurate, or perhaps approximately true would be a better description. Things happened pretty much as I've said and the numbers and names are generally pretty close but this is not intended to be basic physics, or even history - it's a generalized description about computers - and the intention is only to give you some background and make you a little familiar with the guts of a computer. For *MUCH* more information, in *MUCH* greater depth, I recommend a good reference such as Scott Mueller's "Upgrading and Repairing PCs" produced by Que Press. On the other hand, if you'd rather have a root canal done - I understand. To each his own.

Back to the basics of microprocessors. The earlier chips were soldered onto the mainboard - solid and safe, but almost impossible to change. Starting with some '386 chips (and most '486 chips), almost all microprocessors now go into sockets - usually ZIF sockets (Zero Insertion Force). A ZIF socket has a little lever along one side - if you release the lever and lift it up, the chip comes right out - lowering the lever locks the chip into the socket. The Pentium-II/III family of chips began with a design that required the use of a slot - similar to an expansion slot - to hold the microprocessor; they now offer ZIF socketed packaging as well.

Another factor of microprocessors is heat. Heat was not a problem with earlier chips; the way they were made allowed enough heat to escape to keep the chips safe. But, starting with the '486 chips, the speeds were pushed high enough that the microprocessors were being worked hard enough to generate enough heat to kill themselves. Enter heat sinks - a common solution for heat generating components. But heat sinks alone were quickly proven inadequate and active heat sinks (heat sinks with cooling fans mounted) became the norm. As microprocessors are pushed to higher and higher speeds, cooling becomes more and more vital. Some design engineers have designed (and are selling) miniature liquid-cooled air conditioning units to keep modern microprocessors cool. All microprocessors today require an active heat sink and the tiny little fan should be checked every so often to make sure it is still doing it's job. The newest mainboards have diagnostic hardware/software built in that will warn you if the heat of the microprocessor rises to a dangerous level and some of them will even monitor the speed of the cooling fan and warn you if it drops below a certain level.

I guess the discussion of microprocessors should end with the different manufacturers that supply today's PC market. The biggest is Intel - it totally dominates the PC microprocessor industry. It's Intel that makes the improvements and designs the next generation of microprocessors. The other big two - AMD and Cyrix - design and build Intel work-alikes. On the one hand, their chips can be good value since they sell a good bit cheaper than Intel chips with very little loss in ability. On the other hand, Intel is still the original - the standard by which others are measured.

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