Tuesday, July 05, 2005

A REALLY Personal Computer

Years before the PC (the so-called Personal Computer) became widely known to households across America, there were a few of us that had really personal computers. In those days, we predicted that someday, computers would be sold like radios and toasters. We called this dream the appliance computer, because it would be just another household appliance. Alas, when the appliance computer arrived, the marketeers called it a personal computer, but it wasn't nearly as personal as what we had before that.

When I began my engineering career in 1959, the first job I had was designing part of a computer. Computers were a roomful of refrigerator-sized cabinets back then. Later, I designed entire computers, and the software that was used to make software. As computers became smaller, I often yearned to have my own. I once designed one that was so small I might afford to build it, but it was really a toy that wouldn't be very practical. Finally, the technology advanced to the point where a few companies made kits that allowed people with the right skills to build a computer that they could afford.

I had already built a few radio receivers and audio amplifiers from kits, so I knew I could do it. The kits included the design drawings, and I also had all of the details for all of the software. So with full knowledge of every detail of the hardware and software, I could customize the design to my liking. For various reasons, I made modifications to both hardware and software, so it was as personal as you could get.

The picture on the left shows the main computer box and its contents: the power supply, one board for the computer chip and essentials, another board for memory (RAM) , and a small board to interface to the keyboard and monitor. There was room to add more memory boards and interface boards.

I also built the keyboard and monitor shown on the left here. All of those keys on the keyboard are actually switches mounted on a circuit board.

The monitor was built with a television tube, and the circuitry handled only text -- no graphics. It could display 25 lines of text 40 characters long. I modified the design to double the display memory. This didn't display twice as much text at once. Instead I put a switch in front that selected which memory to use.

There was no hard drive, and no floppies. The only permanent (power-off) memory was a pair of ordinary audio cassette recorders. The box shown on the left here, also built from a kit, interfaced the computer to the audio recorders. The data rate was only 300 bits per second, so when it was time to load or store a program or data, you started it, took a coffee break, and hoped that it went OK. I modified this design, too.

When I finally made the transition to a new appliance computer (a.k.a. "PC"), it seemed strange to be using a computer that held hardware and software secrets. Something like driving a car that you're not allowed to look under the hood.

And for a few years, the media didn't dare mention words like "floppy", "software", etc, assuming that this was some realm of specialized knowledge, like Markov Analysis, that most people would have no idea about. Then they suddenly realized that there were many households with PCs, and it was OK to mention them to the general public.

1 comment:

JC said...

For the background and history of the SWTPC computer kits, see