A programmer who goes by Frntc, or Carsten, managed to run DOOM on the original Commodore 64 with a Raspberry Pi-powered expansion cartridge. This RAD Expansion Unit basically emulates RAM expansion and boosts CPU power on the C64, thanks to a Raspberry Pi 3A+, 3B+ or Zero 2 W. It takes over the C64’s MOS Technology 6510 / 8500 CPU and can emulate up to 16MB of RAM, which is a big step up from the factory 64KB of RAM.
There’s just one downside, and that is the C64 still uses its graphics chip, VIC-II, to show the DOOM tech demo. It’s capable of displaying 16 colors (320 x 200 pixel resolution), but can still run the game at 50 fps. As for sound, there’s the SID (Sound Interface Device) sound chip, which plays back 22050 Hz samples. All that’s left is to connect a computer mouse to the Commodore 64 for the authentic DOOM experience. Download it here now.
- Raspberry Pi Zero W (Wireless) Board with on-board WiFi and Bluetooth
- CanaKit Premium Black High-Gloss Raspberry Pi Zero Case
- Includes Samsung 64 GB MicroSD Card (Class 10) - Pre-loaded with NOOBS
The transfer of the audio stream is handled using an interrupt running on the RPi, except during DMA transfers (e.g., copying the frame buffer data) where writes to the SID/Digimax are manually timed. The MIDI output is sent at 50Hz together with the image,” said Carsten.
