[ebruchez]

One of the interesting aspects of the Altair was that it was based on a bus called the S-100 bus. You would have a CPU card and a memory card at least, but everything else was optional. The serial board was separate, and strictly not absolutely necessary to play with the computer, since you could enter simple programs directly from the front panel.

[SoftTalker]

I remember S-100 from when I was a kid. Never was hands-on with that hardware but there were all kinds of ads for cards in Byte magazine and others. Seemed like you could get a card for almost anything in S-100 protocol.

[ebruchez]

That's right. There are still S-100 enthusiasts who are maintaining and developing S-100 cards, see http://www.s100computers.com/ (does not seem to respond correctly to HTTPS right now).