* The 6502 core used inside the [[NES]] is missing the Decimal Mode feature.
* The 6507 CPU, used in the [[Atari VCS]], has only 13 address lines. So it can only address 8KB instead of 64KB. It also lacks the IRQ and NMI interrupt lines. [https://youtu.be/qvpwf50a48E Atari VCS - : The Ultimate Talk] [https://cdn.hackaday.io/files/1646277043401568/stella.pdf Stella programmer's guide]
* The 6510 CPU, used in the [[Commodore 64]], is a 6502 with an additional AEC pin that puts the bus in high impedance mode. It also includes a 6-bit I/O port that occupies addresses 0 and 1.