Instead of going with silicon-based switching (ie: transistors) this 4-bit adder uses mechanical relays. We like it for its mess of wires (don’t miss the “assembly” page which is arguably ...

MikroLeo is a discrete TTL logic-based microcomputer intended ... at the Brazilian Federal Institute of Paraná, Brazil. The 4-bit CPU has a Harvard RISC architecture built entirely from 74HCT ...