Hmm... in this case, you might be right. You'd then need to advance 2 registers by 8 each time, and you'd be paying an extra 3 T-states per compare for the fetc

Hmm... in this case, you might be right. You'd then need to advance 2 registers by 8 each time, and you'd be paying an extra 3 T-states per compare for the fetch of the immediate operand, but you'd be saving 4+ cycles in various places from never needing a DD prefix... (Actually, MIN_X and MAX_X are supposed to be values you fetch from memory, as you can see from the 6502 code. I have no idea why I wrote what I did for the Z80 version. You could use self-modifying code to put constants in the right place, though - which, thinking about it, is actually what I should have done for the 6502 version.)