* The 6510 CPU, used in the Commodore 64, is a 6502 with an additional AEC pin that puts the address bus in high impedance mode. It also includes a 6-bit I/O port that occupies addresses 0 and 1.
* Similarly, the The 6502C used in Atari 8-bit computer range, adds an additional HALT pin. The 6502C is otherwise a regular NMOS 6502, not to be confused with the CMOS 65C02.
* The CMOS 65C02 fixed multiple bugs of the original NMOS 6502, but also removed access to all illegal instructions. Some cycle counts have been modified and some extra instructions have been added. In fact, there are multiple implementations of the 65C02 (WDC 65C02, WDC 65C02S, Rockwell R65C02, CSG 65CE02, ...), each with its own variant of the instruction set.