I've wanted to build a relay computer since forever. My backplane and card design is heavily influenced by the S-100 era (Altair/IMSAI) to make it a plug-n-play machine. The architecture is based on that of Dr. Harry Porter, although I'm going to take some cards in a different direction because...why not?! And I'm using an Arduino to do some automated testing along the way.

This relay computer project is based on the designs of Dr. Harry Porter, who designed and built a multi-wall sized fully functional relay computer at Portland State university. Dr. Porter was gracious enough to share much of his designs which can still be found on the internet. I've also been leveraging the work of Paul Law, who built a relay computer based on Dr. Porter's design, and he shared much of his design in detail. Most of the popular relay computer designs owe a debt of gratitude to Konrad Zuse who built the first relay-based computer (with 2600 relays) by 1941.

When we say relay "computer" - it's more like relay "central processing unit". The architecture is as follows:

The A - D registers are 8 bits, and then we others like M1 + M2 that can be combined to a 16-bit M register. These 16-bit ones are used to leverage addresses for jumping or returning to specific memory locations.

So to make a working clickity unit, we'll need: