The two open I/O slots are for general purpose user I/O, special purpose I/O cartridges (such as IEEE), and have been tentatively designated for enabling the Z-80 cartridge (CP/M option) and for interfacing to a low-cost high-speed disk system.

The system provides for "auto-start" of the program in a Commodore 64 Expansion Cartridge. The cartridge program is started if the first nine bytes of the cartridge ROM starting at location 32768 ($8000) contain specific data. The first two bytes must hold the Cold Start vector to be used by the cartridge program. The next two bytes at 32770 ($8002) must be the Warm Start vector used by the cartridge program. The next three bytes must be the letters, CBM, with bit 7 set in each letter. The last two bytes must be the digits "80" in PET ASCII.

COMMODORE 64 MEMORY MAPS

The following table lists the various memory configurations available on the COMMODORE 64, the states of the control lines which select each memory map, and the intended use of each map.