From: John Forecast <john at forecast.name> [E11 on MIM] Just the control registers. I hate doing an emulation of a speed-up feature which actually slows it down (which is the case with the FASTBUS: emulation for dual PDP-11/45s but there was no way around that -- making the memory inherently mP-safe meant dinking with locks on every access, so it's *much* slower to touch it than non-"FAST" core). It might be interesting to do as a SET CPU option though, for testing how code would behave in nasty cases on a real 11/74. The fetch/decode/dispatch loop and the most common instructions are recompiled (from scripts) on every SET CPU command, so options like this can be added without penalty, as long as they're disabled by default. It'd be pretty painful though, since in this case *anything* that touches memory would have to be compiled at runtime, so it'd be a lot more code than it is now (less common instructions are static and check the SET CPU flags themselves on the fly rather than having their behavior hard-coded into the compiled code). John Wilson D Bit