The C64 CP/M implementation required the Z-80 cartridge which contained an actual Zilog Z80 processor that took over when CP/M was running - the 6502 would esse

The C64 CP/M implementation required the Z-80 cartridge which contained an actual Zilog Z80 processor that took over when CP/M was running - the 6502 would essentially go idle while the Z80 accessed the C64's memory and peripherals.