[Simh] pdp11 fails MAINDEC CPU test 14 D0NA

[Paul Moore]

Not sure if you are interested but I found that simh fails test 14. (Running the tests on my own emu project and wondered if simh would pass all of these nasty tests too)

007176: 010700                              mov       r7,r0                                       ; @.
007200: 012700 006340               mov       #6340,r0                               ; @.`.
007204: 010020                              mov       r0,(r0)+                 ; ..
007206: 026727 177126 006342                 cmp       6340,#6342                         ; W-V~b.
007214: 001401                              beq        7220                                       ; ..
007216: 000000                              halt                                                        ; ..

If you don't know these test the general layout is as follows
Load pc in r0 (presumably to identify the test if a halt occurs)
Run the test
Halt if fail
Next test

Simh halts at 7220

This test is verifying the behavior of using the contents of an auto increment register. IE exactly when does the register change value in the instruction flow

Mov r0,(r0)+

Their test expects the value moved to DD to be the new value of R0. Ie the incremented register value is committed as soon as it is used to calculate the address
Simh(v4) (running as 11/05 not tried other models) moves the old value. Ie the register update is not processed until the instruction is complete

sim> e r0
R0:     006342
sim> e 6340
6340:   006340


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