From: Matthias Buelow <mkb@mukappabeta.de>

>A dedicated microcoded "illegal" op, i.e., which
>is then trapped and implemented in microcode would probably
>be a lot more towards correctness than heuristically guessing
>something in some code seemingly specific sequence...

How about doing it as a device rather than an instruction?  Idle loop touches
a device which real VAXes wouldn't have, but which SIMH can be configured to
emulate by yielding the time slice, or doing a sleep, or whatever.

John Wilson
D Bit