Back to the BASICs with FPGAs

With a little help from a nearly twelve-year-long manufacturing run that would be unheard of today, the Commodore 64 still reigns supreme as the best-selling desktop computer model of all time. Because of its popularity and longevity, it is the first personal computer that many people owned. For this reason, many of us still have fond memories of the machine and long to see its dark-blue background and light-blue border and text that appear on power-up from time to time.

Fortunately, with as many as 17 million units having been sold, there are still plenty of operational Commodore 64s available on secondary markets for pretty reasonable prices. The earliest machines are about to turn 43 years old, however, and that means crucial components like the VIC-II video chip and the SID sound chip are more likely than ever to fail. Components such as these have not been manufactured for a very long time, so retro computing enthusiasts will eventually have to learn to get by without them.

One option is software emulation, but no vintage computing purist is going to accept that as anything like an authentic experience. Reproducing the hardware with an FPGA is another option, and while it may not be exactly the same as the real silicon, you would be hard-pressed to spot any differences if the circuit is well-designed. These FPGA-based solutions can either serve as drop-in replacements for failed chips, or they can emulate the entire computer.

GitHub user joachimdraeger has taken the latter approach, but the project is still a work in progress so not all of the hardware is available yet. For now the design, called VIC64-T9K, emulates a 6502 CPU, the VIC-II video chip, and 64KB of RAM. That leaves out the all-important SID chip, and the Complex Interface Adapter chips that handle I/O, for instance, but even so, what is included is enough to do a whole lot of retro computing.

Perhaps these few shortcomings will be more excusable considering that VIC64-T9K runs on a Sipeed Tang Nano 9K FPGA development board, which can be purchased for 20-ish dollars. Not a bad way to get your retro computing fix, huh? And since the board has been designed to output an HDMI video signal, you won’t even have to search for adapters or dig an old TV out of your attic.

If you want to try it out for yourself, joachimdraeger has some instructions available to help you get up and running. Or if you wouldn’t mind waiting a bit longer for an authentic, Commodore-branded FPGA-based Commodore 64 clone, then be sure to check out the Commodore 64 Ultimate.