8-Bit Computer
Ben Eater's breadboard-computer series and Malvino's Digital Computer Electronics got me curious about what actually happens between an instruction hitting a register and a value showing up on the bus. I redrew a version of the machine in Logisim and started laying it out as modular 7400-series KiCad boards.
The architecture has an 8-bit shared bus, general and interface registers, a program counter, program memory, an instruction register, an ALU built from slices, and microcoded control logic. In simulation it's Turing-complete, and I wrote machine-code and custom-assembly programs to exercise it. The clip below runs one: load 4, add 13, output the result.
I didn't finish assembling the boards into a physical machine. The Logisim model runs the programs; the KiCad files were the next step.
General-register PCB render:
Program-memory PCB:
ALU schematic:
