@douga There's a very famous solution that's been around for a long time called Keyrah, you can check it out here http://www.vesalia.de/e_keyrahv2.htm . I know the C64 runs quite well on VICE but because it's such a famous machine there are better solutions around in FPGA if your life depends on a good modern version of the C64 in your original case. No real need to software emulate this one.