Quantum 64 is a harsh and aliased digital synth with single DCO and multimode filter.
It is inspired by Commodore 64’s SID soundchip but it definitely is no emulation. The two special ingredients that make the soul of Quantum 64 are the arpeggiator and the degrader/quantiser unit. By the way, those patches named by the classic game names have very little or nothing to do with the sounds of the original games…