MOS Technology 6510

The MOS Technology 6510 is a microprocessor designed by MOS Technology, Inc., and is a modified form of the very successful 6502.

The primary change from the 6502 was the addition of an 8-bit general purpose I/O port (only six I/O pins were available in the most common version of the 6510). In addition, the address bus could be made tristate.

The 6510 was only widely used in the Commodore 64 home computer (and in significantly smaller numbers in the C64's portable version, the SX-64). In both the C64 and SX-64 the extra pins of the processor were used to control the computer's memory map by bank switching, and in the C64 also for controlling three of the four signal lines of the Datassette tape recorder (the electric motor control, key-press sensing and write data lines; the read data line went to another I/O chip). It was possible, by writing the correct bit pattern to the processor at address $01, to completely expose almost the full 64KB of RAM in the C64, leaving no ROM or I/O hardware exposed except for the processor I/O port itself.