* Conditional jumps are only 8-bit relative. And unconditional jumps are only 16-bit absolute.
* The 6502 post-decrements on PHA and pre-increments on PLA, while the Z80 pre-decrements on PUSH and post-increments on POP, making them behave in opposite ways.
* The 6502 uses only one addressing mode per instruction, while the Z80 can combine two different addressing modes within a single instruction.
* The 6502 saves flags automatically during interrupts; while the Z80 requires PUSH AF and POP AF.
* The 6502’s Decimal (BCD) mode automatically adjusts ADC and SBC results, while the Z80 requires a DAA instruction after each BCD addition and subtraction.
* ADC is the only command for addition. To perform an addition without carry, the carry flag must be cleared manually first. Same with SBC for subtract.
* The alternate NOPs are not created equal. Some have one- or two-byte operands (which they don't do anything with), and they take different amounts of time to execute.
* The 6502 post-decrements on PHA and pre-increments on PLA, while the Z80 pre-decrements on PUSH and post-increments on POP, making them behave in opposite ways.
* The 6502 uses only one addressing mode per instruction, while the Z80 can combine two different addressing modes within a single instruction.
* The 6502 saves flags automatically during interrupts; while the Z80 requires PUSH AF and POP AF.
* The 6502’s Decimal (BCD) mode automatically adjusts ADC and SBC results, while the Z80 requires a DAA instruction after each BCD addition and subtraction.
<br>