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Twenty Years Ago, Part 4 - CPU

part 3 - disk storaage

ENIAC (electronic numerical integrator and computer), the first electronic digital computer, had about 19,000 vacuum tubes and hundreds of thousands of resistors, capacitors, and other components, and consumed nearly 200 kilowatts. Vacuum tubes were nowhere near as reliable as solid state components, and the vast number meant that some of them burned out every day, so it was almost a full time job just keeping the thing going.

Despite its size, ENIAC wasn't a very smart computer by today's standards. It could do simple math, and extract square roots, but it could store only twenty 10-digit numbers. Still, it could do in 30 seconds what a person with a desk calculator could do in twenty hours. Not bad for a dumb machine!

The first solid state personal computers weren't much of an improvement over their vacuum tube predecessors; all had to be programmed to do even the simplest of calculations. Input was done by setting switches, and output was by means of lights or meters, which had to be interpreted to get the answer to the question.

It wasn't until the 1970's that practical computers became available for personal use. When I bought the QX-10, the dominant chip was the Zilog Z-80. One way to classify CPU chips is by the size of the pieces of information it processes. The Z-80 was an 8-bit chip, meaning it could process a piece of data 8 bits in size.

"Okay, what's a bit?" you ask. Computers "think" in binary, or base-2 numbers. Instead of the ten digits we use for math, the computer uses only two digits, a zero and a one. Though difficult for humans to use, this system is convenient for computers, as a simple switch or other on-off device can be used for each digit. Switch off - zero. Switch on - one.

At any rate, most computers use binary math, and most personal computers are classified by the number of bits they can process. While the QX-10 and the IBM PC could process 8-bit data, today's computers can take information in 32-bit chunks, so each process potentially can handle four times as much information.

That's a nice increase, but the real development has been the processing speed. That smokin' Z-80 in my QX-10 would perform about four million operations per second (4 megahertz, or 4MHz). The first common Intel chip, the 8080, was about the same. In the last couple of years, the plain-vanilla home computer has passed the gigahertz (GHz) mark, now performing billions of operations each second.

For a long time, it seemed that as soon as a more powerful chip was released, software would expand, and computers could not keep up with software demands. That has changed, now, depending on the applications you use. For those of us who are mostly pushing words, a relatively slow 333 MHz computer works about as well as one running at 3 GHz. The real pressure now comes from graphics-intensive programs like CAD, but even more from games. Those animated action games that portray lifelike characters moving in real time take a lot of power!

2003 Sheldon Wolfe, RA, FCSI, CCS, CCCA
on the web at www.CSI-MSP.org


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