Dr. Scott M. Baker Turns His Intel 8008 CPU Board Into a True, Back-to-Basics Single-Board Computer
128kB of RAM, 128kB of ROM, serial, and a display card with backlit keypad and complex sound generator give the Intel 8008 a swish home.
Maker and vintage computing enthusiast Dr. Scott M. Baker has designed a single-board computer built around what is generally understood to be the world's first eight-bit programmable microprocessor: the Intel 8008.
The exceedingly-retro single-board computer build was inspired by Baker's earlier work on creating a "downgrade" board for his Heathkit H8, which replaced the device's original Intel 8080, released in 1974, with the earlier and binary-incompatible Intel 8008. Having built an Intel 8008 CPU board, then, adding the rest of the computer seems a logical next step.
"I decided to take that design and translate it back into a single board computer, with an optional display board," Baker explains. "At the same time, I made a few improvements, for example increasing the banked memory support from 32kB RAM/ROM to 128kB RAM/ROM. Now, we don’t really need all that RAM, but the ROM is useful to store additional programs that may be bank switched in."
The computer itself fits on a single board, making it a true single-board computer, though display and input take up a second board — offering the seven-segment numerical LED readouts and hexadecimal keypad inputs common to computers of the era, though with the added bonus of a buzzer linked to a complex sound generator with three voices and a noise engine and very swish LED backlights to the keys.
"Several Programmable Logic Devices (PLDs) are used to handle bus signals, IO [Input/Output] addressing, interrupt support, etc.," Baker writes. "The PLDs used are GAL22V10D. Each one replaces about a half-dozen discrete logic chips, vastly reducing board size and component count. There’s nothing magic in them — they’re just plain ordinary logic comprised of your typical ANDs and ORs and such."
On the software front, the machine supports Baker's customised 8008 Monitor, based on an earlier program written by Jim Loos, Scelbi Basic, Baker's Jonesforth port 8008-Forth, and Galaxy, a clone of the classic Star Trek game written in 8008 assembly.
Baker's full write-up is available on his website, while design files and source code can be found on GitHub under an unspecified license.