Oh, I missed an instruction for de-stacking the arguments, which was typically something like 'add #N, sp', so another two instruction word fetches, or 43 cycles. Ironically, if N=4, the compiler used to emit a 'cmp (sp)+, (sp)+', which is more efficient space-wise (one word instead of two), but less time-wise (3 cycles instead of 2). Noel