MOS Technology 6510

The MOS Technology 6510 is an 8-bit microprocessor designed by MOS Technology. It is a modified form of the very successful 6502. The 6510 is widely used in the Commodore 64 (C64) home computer and its variants. It is also used in the Seagate ST-251 MFM hard disk. The primary change from the 6502 is the addition of an 8-bit general purpose I/O port, although only 6 I/O pins are available in the most common version of the 6510. In addition, the address bus can be made tri-state and the CPU can be halted cleanly. The 6510 and variants were based on the same core as the 6502, and are opcode compatible, including undocumented opcodes. The parallel port was provided by using several formerly unused pins, eliminating some, and re-arranging others. In the original 6502, pins 5, 35 and 36 were not connected. Pin 3, formerly the phase-1 clock out, was eliminated, as most roles did not require it.