|YEAR OF INTRODUCTION||1976|
|CLOCK SPEED||4 MHz|
|FLOATING POINT UNIT||none|
|MEMORY MANAGEMENT UNIT||none|
|OPERATING SYSTEM||CDOS and CP/M|
|HONOURABLE MENTION||Bores Marczuk|
Way back in the mid 1970's before I was born, when the closest thing to a personal computer was the PDP-8/e, Ed Roberts of MITS created a computer kit known as the Altair 8800 based around the Intel 8080 CPU. In the process he created a computer bus based upon the availability of inexpensive surplus 100-pin edge connectors. This bus was quickly adopted by the DIY community and later became known as the S-100 bus.
And the MITS Altair 8800 begat the IMSAI 8080; and the IMSAI 8080 begat the Cromemco Z-1; and that is where I'll stop...
I got this machine while working at an electronics store around early 2001. I had left an 8" floppy on the counter and a customer saw it. He mentioned that he had an old machine sitting in his garage that used them. I asked him what it was and his reply was something to the effect of "I don't remember but it has a lot of lights and switches on the front".
Those magic words again: LIGHTS AND SWITCHES!!!
I asked if he were willing to sell it and he said yes. He brought it to the shop the next day and offered it to me at $50 which I gladly accepted.
When I first got it, the leftmost switch paddle was missing but it has since been replaced. Most of the photographs, except the one above, were taken before I got the switch paddle.
Basically this machine is an IMSAI 8080 with a Cromemco backplane and cards, and different front panel artwork. There is an incompatibility between the front panel and RAM board so I am unable to program it via the binary switches. This is due to using different signals for memory write which were not standardised at the time the front panel was manufactured. I made a few modifications to the panel to bring it in line with the IEEE standard but not the way it writes to RAM.
Before I left Melbourne, I purchased a couple of S-100 wire wrap boards. I designed a static RAM board with banking and active bus termination but didn't get around to building it as I found myself needing to go to Scotland.
Now, after 2 years of being back in Melbourne, I've decided to pick up where I've left off and restore this machine beyond its former glory. I'm scouring eBay for S-100 cards to beef this little puppy up. Fun, fun, fun...
One of the latest additions to this machine is a 32k Static RAM board. I purchased a PCB for the Salota Mixed Memory card from eBay. It was designed to take sixteen 2k static RAM chips but I modified it to take one 32k chip on a daughter board. At some point I may put some additional RAM and/or ROM on it, but this isn't really of high priority as 32k should be sufficient for the time being.
Coming soon: Ithaca Audio Display Card kit. Hotcha!!!
For further reading on the subject of S-100 machines, I recommend checking out the S-100 Computers website as it has a wealth of information and photographs.