A Commodore 64 with a RAD expansion unit

Raspberry Pi Powers Commodore 64 Expansion Cartridge, Plays Doom

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Commodore was a big name in the 1970s, 80 and early parts of the 1990s. Its range of home computers spanned the decades, but one, the Commodore 64, shines just a little brighter than others. Frntc aka Carsten has devised a Raspberry Pi-powered cartridge, RAD Expansion Unit, which emulates a RAM expansion and provides a CPU boost for the 40+ year machine. And the classic means to test it has to be “Does it run Doom?” Well it does, but the Raspberry Pi is doing most of the heavy lifting. Still,  the graphics and sound are all thanks to the Commodore’s custom chips.

The RAD Expansion Unit connects to the Commodore 64 (or 128) cartridge port and uses a Raspberry Pi 3A+, 3B+ or Zero 2 W to emulate a RAM expansion unit of the era. It also bypasses the main MOS Technology 6510 / 8500 CPU (running at a mighty 1.923 MHz for NTSC, and 0.985 MHz for PAL) to provide the full power of the Raspberry Pi’s Arm CPU. RAD can emulate up to 16MB of RAM, many times the original 64KB of RAM on a stock model. This means that RAD provides the horsepower to play a Doom tech demo, but we can only see it thanks to the onboard graphics chip, VIC-II. 

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