I/O and memory access are the same thing for the 6502. All it can do is read or write from a bus with 16 address bits and 8 data bits. The environment/motherb

I/O and memory access are the same thing for the 6502. All it can do is read or write from a bus with 16 address bits and 8 data bits. The environment/motherboard might have memory that responds to some combinations of those address bits, and it might have something like say an NES PPU that responds to other combinations, by handling those writes as tile or sprite data and generating a video output signal. You could hypothetically make a 6502 with a wider or dual bus, so that it could read or write more than one byte per cycle or both at the same time, if whatever else is on the bus on the other ends of the reads/writes is compatible with that. In that way you could speed up executing 6502 instructions by more than just increasing clock speed.