The schematic wasn't in the C64 User Guide delivered with the machine, but it was in an additional Commodore publication "Commodore 64 Programmer's Reference Gu

The schematic wasn't in the C64 User Guide delivered with the machine, but it was in an additional Commodore publication "Commodore 64 Programmer's Reference Guide". The PRG was essential if you wanted to do anything more than the most basic BASIC contained in the UG. See p.514- for the schematic https://archive.org/details/c64-programmer-ref/page/n513/mode/2up https://archive.org/details/c64-programmer-ref/page/n513/mod...