[Simh] DECsys-7 on SimH [was Re: new paper on history of Unix]

dott.Piergiorgio dott.piergiorgio at fastwebnet.it
Sat Aug 21 17:59:35 EDT 2010

Il 21/08/2010 02:37, Rich Alderson ha scritto:

>> after looking at PDP-7 DECSYS (aside that seems that can't works on SIMH
>> because of the DECTape track mark issue)
> Have you tried it?  I just did, following Bob's instructions in the doc.txt
> file included in decsys.zip on the SimH software page.  See below.
> Remember that the DECtape images used by SimH are data-only, and assume
> standard format tapes (578 blocks of 256 18- or 16-bit words or 128 36-bit
> words, or 1100 blocks of 129 12-bit words).  The difference between a PDP-7
> DECtape and other systems' is in the overhead frames, not in the data.

Yes, I have no issues in booting & running DECsys-7, the real issue is 
that the assembler and fortran compiler don't work, and the latter, 
IIRC, entering an infinite write loop on the scratch tape (for sure, I 
find a multi-megabyte scratch tape after the ^E) I suspect that this was 
'cause both program look for the  marks in the scratch tape(s)

(as hinted in some of my past post, my main interest in emulation 
at-large, well, is homebrewing new code...)

ah, in assembling & comiling I have followed the DEC manual of the 
DECsys-7, whose is in the good ol' Kossow's now huge bitsavers archive :)

> (As it happens, Prof. Harlan Lefevre was here at the museum last week, to
>   give us a hand with the PDP-7.  Bob's notes, written in 2006, mention that
>   we would be putting the system on-line "soon"; 4 years isn't that bad.)

well, when the -7 finally boots, I hope will be tried some test 
assembling & compiling and a check of the actual state of the track 
marks on physical scratch DECTapes after an assembling & compiling...

For now, I'm scratching the head ;)

Best regards from Italy,
dott. Piergiorgio.

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