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Wiki
zimmers.net
C64/C64C Service Manual
A brief history of C64

Please compare with its predecessor Commodore C64 and take a look at 1541 FDD.

C64G combines an old C64-style case upgraded with a new motherboard shared with C64C. The chips on board are also new revisions of the ones in C64 and some of them are not electrically or pin-compatible (e.g. VIC-II uses different voltages and can be probably damaged by putting into C64).

Internals

Motherboard

Keyboard

There were also C64G sold with a dark keyboard, but they were much more rare.

Reassembly