View Full Version : Building an S-100

April 11th, 2015, 05:13 PM
First, I'm fully aware of N8VEM.

How insane am I to be seriously considering building an S-100 compatible from scratch? I just want to get a realistic idea from you folks. I already have a working Z80A on a set of breadboards that can single instruction step (vs. single clock step.. not useful unless there's something seriously wrong) and run on a 2 MHz crystal that successfully reads and begins executing from an EEPROM. Needless to say, this is a very long way from a set of boards plugged into a backplane. :)

My motivation is manifold. First, I absolutely love front panels. I've started sourcing out some switches and such to make something IMSAI-ish/DEC-ish. I prefer the paddle covers over the toggle switches rather than the Altair look. Second, I find it's a phenomenal learning experience. I teach assembly language courses for penetration testers and reverse engineers. Building something from this point of view is very good experience to me. A third motivation is that I love retro/vintage computers (and have quite a stack) but I just can't bring myself to shell out > $1,000 for an IMSAI or Altair or PDP in very questionable condition... Forget $2,000+ for something sorta working. :)

My thought on being S-100 compatible is just the possibility of interfacing other things from existing stock and even the possibility of manufacturing some systems if there turns out to be interest after the prototype is done. It makes sense to me to build to a bus standard that exists rather than reinventing the wheel and being completely incompatible (like my trusty TRS-80 Model II).

So... Is this insane? Am I looking at thousands of hours or merely hundreds? What are your thoughts? I was actually quite surprised at how quickly things went together to get what I have mocked up on breadboards.

April 13th, 2015, 08:23 AM
You could do what I'm attempting: Buy an AltairClone for $650 to give you an attractive enclosure and front panel, then all you have to do is review Mits' diagrams to wire it into an S100 bus.

April 13th, 2015, 09:27 AM
I suggest that you take a look at http://www.s100computers.com/. They have a significant number of s-100 boards designed and available that you can build up yourself. These are available on an ongoing basis, so you may have to wait a bit for some of them to go into a new run, but you should be able to get a very decent S-100 system built up pretty much on your own timeline. Also, there's nothing holding you back from mixing in some "real" vintage S-100 boards that might come up for sale elsewhere, too.

Good luck!