C64 Hardware Simulator: Break Chips, Watch Results
Original: The Commodore 64 hardware simulator: break chips and pins, see the results
Why This Matters
Pin-level hardware simulation bridges retro education and real diagnostic methodology.
Developer antirez released c64-hw-simulator, an open-source pin-level Commodore 64 motherboard simulator (ASSY 250407) that lets users lift chip legs, short pins, or pull chips to observe realistic hardware failure behavior.
Antirez, the creator of Redis, has released c64-hw-simulator on GitHub — a pin-by-pin simulation of the Commodore 64 ASSY 250407 motherboard. The tool models the board's full netlist and individual chip behavior, allowing users to lift pins, short them to ground or +5V, pull chips from their sockets, or open resistors — then watch what happens on the simulated display, keyboard, and signal lines.
The simulator's key claim: it doesn't know in advance what a broken C64 looks like. When a fault is introduced and the screen fills with garbage, that output comes from circuit computation alone. One documented example involves lifting pin 17 (A7) of the color RAM before power-on. The machine boots looking healthy because the CPU and VIC both write and read from the same wrong address, causing aliasing. Restore the pin, and the uninitialized half of the color RAM appears as random colors. Lift it again, and the screen clears. The author notes a real 2114 chip behaves identically.
The project has attracted 321 stars and 11 forks since launch. Its stated goals are education and hardware fault analysis — letting users understand how the C64 works at the electrical level without owning or risking physical hardware.