On Sun 29 Jul 2018 at 10:42:19 +0000, Lars Brinkhoff wrote: > I have a very small debugger for the GT40 called URUG, or micro RUG. It > has two troublesome instructions: CMP R3,(R3)+ and equivalent with R4. > I suppose SIMH will run it fine even though there's a hazard?
In the "PDP-11 Architecture Handbook 1983-84" (EB-23657-18) there is a convenient appendix listing the differences between various implementations of the PDP-11. OPR %R,(R)+ is listed as case 1. The difference between cases is whether R is incremented before using it as the source operand. Apart from that no issues are listed, so if you don't care about that difference there is no problem. > Would there be any possible downside to using TST (R3)+ instead? Both instructions affect all 4 flags, so no code can already depend on preserving any. -Olaf. -- ___ Olaf 'Rhialto' Seibert -- Wayland: Those who don't understand X \X/ rhialto/at/falu.nl -- are condemned to reinvent it. Poorly.
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