8

The Altair 8800 was based on what came in later years (much to the displeasure of MITS) to be known as the S-100 bus, because it had 100 lines, because MITS found 100-pin edge connectors were available cheaply.

Why were 100-pin edge connectors available cheaply? What were they used for before then? Were they some kind of de facto industry standard, was there some particular machine that used a lot of them, or was it just a random one off event that someone happened to be liquidating a few crates of them?

2
  • 1
    much to the displeasure of MITS Now you've got me curious why. – ssokolow Nov 11 '20 at 7:45
  • 1
    @ssokolow Ed Roberts, founder of MITS, thought of the system as 'his' and was not pleased by the quick profusion of companies making add-in boards and clone computers; he saw their insistence on calling it the S-100 bus rather than the Altair bus, as adding insult to injury. – rwallace Nov 11 '20 at 22:12
12

As Wikipedia says (S-100 bus):

"(Author) then looked for an inexpensive source of connectors, and he came across a supply of military surplus 100-pin edge connectors. The 100-pin bus was created by an anonymous draftsman, who selected the connector from a parts catalog and arbitrarily assigned signal names to groups of connector pins."

So the prime reason is "a military surplus". I guess they were used in some army projects in the '70s, like TTL-based mainframes, but I cannot find any evidence for such a claim, as the military computers are not wide-known.

2
  • 7
    In the late 1970s I worked for a So, Calif. based aerospace company and they had a "surplus sales" store on-site. At one point boxes full of 1000s of these 100 pin "S-100" connectors came into the store. As I recall they were quite popular as homebrew was a thing at that point in time. I do also recall seeing them in various pieces of test equipment that were built by the company. I get the impression that these were just generally useful connectors. – jwh20 Nov 11 '20 at 15:31
  • 4
    Computers wouldn't be the only, or likely primary, use of these 100-pin connectors. They would've been used in all sort of electronic devices. – user722 Nov 11 '20 at 16:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.