Has Anyone Written PDP-8 .XOR. Code Using the MQ Register (Without the EAE)?

[Christian Gauger-Cosgrove]

On 23 December 2015 at 13:44, CLASystems <clasystems at gmail.com> wrote:
> Ironically, the shortest and fastest seems to be avoidance of the MQ
> altogether [thus making it work on ANY model].
>
>     TAD  ARGONE
>     AND  ARGTWO
>     CLL RAL
>     CIA
>     TAD  ARGONE
>     DCA ARGTWO
>
> This works because .XOR. is addition ignoring the carry bits.  So, knowing
> they will happen, just allow them at first, then remove them.
>
Hmm, I just tried that in SIMH, and that doesn't XOR at all. I haven't
a clue what it does.

What I have entered:
sim> ie -m 100-105
100:    TAD 76
101:    AND 77
102:    CLL RAL
103:    CIA
104:    TAD 76
105:    DCA 77

Locations 076 and 077 being ARGONE and ARGTWO respectively, at the start:
sim> ie 076-077
76:     1234
77:     4321

After running the above code sample:
sim> ie 076-077
76:     1234
77:     0574

If we "flip" ARGONE and ARGTWO's values (to 4321 and 1234 respectively):
sim> ie 076-077
76:     4321
77:     3661

Neither of those is the expected 5115 of an XOR operation.

Am I missing something blindingly obvious?


Cheers,
Christian
-- 
Christian M. Gauger-Cosgrove
STCKON08DS0
Contact information available upon request.