I agree with Daniël Mantione. I have Commdore 64c with real disk drive 1541-II so yes...I don't care at all for backward compatibility that much for mega65. If it can achieve 50% of software and even then it may seem little fast due to faster CPU speed I am 100% fine with that. I am getting mega65 for future mega65 software and games honestly not for backward compatibility.
So the author of mega65 please, please don't put focus on compatibility that much and waste development time on that. Focus on mega65 basic v10 and it's hardware...I have a c64 here, I have vice if I need it..don't worry we have what we need for c64 software library.