NOP on HP-41C

[hth]

(12-28-2020 08:59 PM)Dave Britten Wrote:  That's pretty close to what I measured, which was about 4 ms. There could be other factors in play that made my program with the message a bit slower - isn't there a slight amount of overhead when program execution crosses a register boundary, or am I thinking of a different calculator? Maybe my program with the "WAIT" message added wasn't aligned as neatly (yes, I PACKed the program, and SSTed over the GTO 00 to compile it first).

That is correct, there program speed may vary slightly due to the position of the bytes inside registers. Not strange if you think about it, it needs to fetch a register and then align the bytes to the same position for execution dispatch. You should not modify the program before the loop, call a subroutine located after the loop where you make any changes.