2026 Retrocomputing Challenge: 16-Bit Homebrew Relay Computer

We did, when we started our retrocomputing challenge. [Peter] decided that transistors weren’t retro enough, and sent us this lovely homebrew relay computer, complete with 16- bit …. 2026 Retrocomputing Challenge: 16-Bit Homebrew Relay Computer.

[Peter] decided that transistors weren’t retro enough, and sent us this lovely homebrew relay computer, complete with 16- bit CPU, which is rather more bits than one normally associates with clicky clacky contacts. The architecture is very simple– it just uses an accumulator register, ACCU, and goes from there. All mathematics and save/load operations go through ACCU.

There whole instruction set is only 19 commands, and he’s used that set to program such lovely things as calculating 3 digits of Pi– which only took 8 minutes of glorious clicking. [Peter] has even implemented a display by hooking his computer to a 32×32 LED matrix, but don’t expect it to relay updates really quickly. If this computer looks familiar, it’s because its earlier incarnation was one of the more “extra” entries in last year’s one-hertz challenge, where it was used to blink an indicator lamp.

Yes, even relay computers apparently get started with the “blinky” sketch.