Peter's Homebrew 16 bit relay computer is a 16-bit CPU built from electromechanical relays. Running a program that calculates pi to two decimal places requires 1,377 instructions and a little over eight minutes. The creator calls it the 'slowest computer in the world.'

It has a 19-instruction set built around an accumulator, and in 2026 gained a 32×32 LED matrix connected as memory-mapped video output.