Some time ago I started looking at a strange (in today's terms) old mini-computer PDP-8 from DEC. It is 12bit machine with one accumulator and program counter, further allows one level of indirection, some models had some memory positions that could be accessed with auto increment and others still had memory paging capabilities.
This mini-computer was so wide-spread that two Integrated Circuit versions of it were produced (IM6100, IM6120) although they came a bit late to a market that progressed beyond the original design.
The book "The Art of Digital Design - An Introduction to Top-Down Design"from Franklin P. Prosser and David E. Winkel describes how to design your own PDP-8 either using normal logic or using a bit slice components, something I would like to build... both versions... :-)
But would I also like to test drive the CPU before I build one, the easy solution would be to find a IM6100 and build it in a bread board... During my search I found that Sparetimegizmos (a company in the US) was selling a kit that included the very hard to find chip! The first time I visited the site it said there were no more ICs, a month ago they had new kits available, so I bought one. They also have front panels but the price tag is bit over my budget, but still very interesting. Here are two pictures the original and the "original copy":
I finished assembly of all the sockets and all the logic ICs, I had some difficulty in finding the IM6402 UART (it is also not cheap), the half-size oscillators, the interface connector and connector that look good on the board, so for now I have a "wrapped version" that I expect to put to work during this week. At least get something on my terminal window :-)
A great thanks to Bob Amstrong and Sparetimegizmos for having the time to design, build and
sell the kit.
2 weeks ago