Reverse engineering circuitry in a Spacelab computer from 1980
Summary
The article presents Ken Shirriff's reverse-engineering of the Spacelab Mitra 125 MS computer’s ALU, explaining how a 32-bit ALU was built from 4-bit 74181-type chips across three boards. It covers the hardware layout, including multiplexers, registers, and carry logic, and places the work in historical context with the Mitra line and Spacelab's replacement by IBM in the early 1990s.