[Simh] pdp-11 id command quirk

Jon Elson elson at pico-systems.com
Wed Jun 15 11:47:37 EDT 2011


Hello,

I want to use the pdp-11 sim of simh to teach my kids some 
machine-language programming.
I have it compiled and running on a Linux system.  When using 
interactive deposit
in the PDP-11 simulator, it increments by single byte addresses, so you 
get :

PDP-11 simulator V3.8-1
sim> id 1000-1004
1000:   1234
1001:   2345
1002:   3456
1003:   4567
1004:   5670
sim> e 1000-1004
1000:   002345
1002:   004567
1004:   005670
so, you see that only every other deposit address actually wrote to 
memory, and the examine
command properly increments by words. If there is a by-word switch to 
the id command, I couldn't
figure it out from the source or help text. (I do see that id -c writes 
2 ASCII characters to even addresses,
and writing assembler mnemonics also works, but numeric values increment 
by one.)

I tried the same thing on the vax780 sim, and it works fine, depositing 
32-bit values on longword
addresses, and then examining them just fine.

If there is an option switch that makes it work correctly, I was unable 
to find that by inspecting the source
or the documentation, or searching the simh archives.

Thanks,

Jon



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