Yes, 5 cycles, good point... that's much better. My excuse for not thinking of this very obvious improvement is that I never wrote any speed-sensitive ROM code

Yes, 5 cycles, good point... that's much better. My excuse for not thinking of this very obvious improvement is that I never wrote any speed-sensitive ROM code ;) I doubt I ever used JMP indirect. For this sort of thing running from RAM, I'd typically use self-modifying code and a JMP absolute, which is where the idea of having a little thunk came from.