C64 has a lot of failure prone parts. Much of that is due to the nature of NMOS construction. You'd want to target large feature size CMOS from the late 80s to

C64 has a lot of failure prone parts. Much of that is due to the nature of NMOS construction. You'd want to target large feature size CMOS from the late 80s to early 90s to hit the sweet spot of semiconductor longevity.