The History of Personal Computing

Heathkit H8

Heathkit was a long established electronics retailer, specializing in build-it-yourself electronic kits. In the wake of Altair’s original move to create a home computer for consumers, Heathkit believed they, too, could capitalize on the homebrew personal computer market. The result was the Heathkit H8 computer, introduced in July 1977. The H8 is similar to other S100 class computers in the sense that it used an Intel 8080 CPU, had a backplane expansion bus, and CP/M was commonly used on it, but the similarities ended there. Heathkit’s engineers noted the need to correct some major flaws in the S100 bus design, like having the +5 volt and ground pins right beside each other. Uncorrected, it was possible to short the power supply if a card was inserted crooked or a piece of metal dropped in the S100 slot at the right position. After all, this was the 70’s. You can’t have one of those low hanging disco chains getting in the works and shorting things out when bending over to insert an S100 card.

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OSI Model 500 (Superboard I)

Ohio Scientific Inc. was a US based computer company that designed microcomputers from 1975 to 1981. The OSI Model 500 system was their earliest system, launched in 1977. It was a very simple single-board computer based on the MOS Technology 6502 microprocessor, but it lacked video circuitry, therefore a serial terminal had to be used. All of the computers that OSI’s went on to design used the 6502. In 1978, they released the Superboard II, also known as the Model 600. It was only available as a ready-built system, although the user had to build or buy a five volt external power supply to power it. The Superboard II included a keyboard, 4K of RAM, BASIC-in-ROM and cost just $279. OSI’s Challenger 1P and Challenger IIP-MF computers used the Superboard II as their main boards. Continue reading OSI Superboard (I and II)…