IMSAI Advert - January 1977

This is another advert for the IMSAI 8080, as used by Matthew Broderick's character David Lightman in the classic nerd-film "War Games". At least when this advert came out the machine was actually new, whilst War Games wouldn't be made for another six years.

It retailed for $931 assembled (about £4,490 in 2024 terms), ran an Intel 8080 and had 22 expansion slots on an S-100 bus, all of which was fed with a 28 amp power supply.

The 8080's style of input, using switches for programming and using lights for feedback, was arguably only of interest to hobbyists and science-types. However it was pretty much the standard for most computers at the time.

Keyboards and video displays were available, but mostly only as expensive add-ons which would be out of the reach of most home users' budgets. The last computer to feature this interface is considered to be 1981's Ithaca DPS1, which is right in to the era of the IBM PC.

The S-100 bus - or Standard 100 - was named after its 100-pin connector. It was first used on the Altair 8800, but its subsequent use on the IMSAI 8080 helped turn it into a cross-micro standard. Many micros of the mid-1970s, and even into the early 1980s, ended up offering the S-100 bus - sometimes with over 20 slots for additional cards.

The job of the S-100 bus was to make the host machine's memory, CPU and other system features, like input/output, available to external plug-in cards. It was originally designed around Intel's 8080 CPU, as that was the processor used on both the Altair and IMSAI micros, but that didn't restrict its compatibility with other processors.

As of September 1978, Personal Computer World was reporting some 150 manufacturers making boards compatible with the "bus of the century^[1]".