« Last post by Dave Turner on Today at 10:52:19 AM »
It was even more complicated than clock speed and clock cycles. If I recall correctly the 6502 was a 2 phase clock whereas the Z80 was single phase and static thus more easily implemented. In general the Z80's plethora of registers (in comparison) made programming at the assembly language level potentially more efficient, particularly because affordable external memory was relatively slow. Nevertheless the 6502's instruction set was more suited to some types of memory addressing; it all depended on what one was trying to achieve.