[its-hackers] Fwd: [PDP-10/its] Use the CH11 Chaosnet address (#2038)

Jack Haverty jack at 3kitty.org
Wed Jun 23 22:44:12 CEST 2021

One other speculation - SAENG may have been "Stand Alone" "Engineering", 
where "stand alone" referred to software used on the machine while not 
running ITS - so that's where DSKDMP would be found.

On 6/23/21 11:26 AM, Jack Haverty wrote:
> Thanks, that all makes sense.   I do remember SEC working on the ML 
> disks; it was very convenient to have another machine around.
> A few observations for historical sake..
> - ENG probably meant ENGineering, which related to "system" stuff, 
> e.g., ITS itself and perhaps major applications like Midas, DDT, Teco, 
> etc.   Everything was in English back then.   ENG in a directory name 
> was an indicator to mere mortals to keep their hands off that directory.
> - When you see things with huge offsets (e.g., JRST MEMSIZ-400), it's 
> likely to be one of two situations.  Either it was an instruction that 
> was patched in using DDT, to jump to code somewhere else that did what 
> needed to be done, usually to clean things up on the way out of some 
> action.  Or it could also have been a jump into a module that had been 
> removed.
> E.g., after Dectapes become obsolete, at one point someone removed the 
> tape-handling code, but didn't necessarily find all of the places 
> elsewhere that had a JRST to some useful section of the tape code.  I 
> remember that we had some bugs in the disk code after the tape code 
> was removed, because it had been written to jump into the tape code 
> where some functionality already existed.
> MIT-DM code did all come from AI.   So it's likely that the DM system 
> utilities like DSKDMP diverged from the AI version, at least for a 
> while, to deal with the unique hardware components in DM (DSK, the 
> E&S, etc.)   That's probably why there was no source code for a while.
> Most of the ITS system utilities originally came from TMRC - the Tech 
> Model Railroad Club, where some of the AI system hackers had built 
> them for controlling the railroad.   I don't remember if there was any 
> effort to archive their software.   But that might be another place to 
> look for really old code.   In addition to migrating to MIT-AI, some 
> of the TMRC people also took it to DEC.
> /Jack
> On 6/23/21 10:12 AM, Lars Brinkhoff wrote:
>> Jack Haverty wrote:
>>> Just curious --- has anyone found source code for DSKDMP?   Back in the
>>> mid-70s, I recall an incident where someone asked for a copy of DSKDMP to
>>> use on some new machine, and was surprised to learn that there wasn't any
>>> source file.   Maybe there once was such a file, but over the years DSKDMP
>>> had been extensively modified and new features added, all by simply writing
>>> new code in DDT and saving the binary image.   So there was no source file
>>> for the DSKDMP we used on MIT-DM, at least at that time.
>> I could well believe this was true at some point.  Unfortunately the
>> backup records are not in a good shape, so we don't have much evidence
>> to go on.  Here are all DSKDMP source files I can see that were backed
>> up on DM.  This is just information from the .TAPE database; we don't
>> have the files themselves.
>>   SAENG   DSKDMP  109    1975-01-15 12:12:12
>>   SAENG   DSKDMP  132    1976-04-23 07:36:56
>>   SAENG   DSKDMP  134    1976-04-24 23:46:12
>>   SAENG   DSKDMP  144    1976-08-09 01:40:50
>>   SYSTEM  DSKDMP  151    1977-04-02 21:00:57
>>   SYSTEM  DSKDMP  155    1978-08-22 02:16:00
>>   SYSTEM  DSKDMP  154    1978-03-16 04:05:16
>>   SYSTEM  DSKDMP  156    1979-09-05 20:45:27
>>   SYSTEM  DSKDMP  157    1979-10-18 06:38:41
>> The first observation I make is that DM stored source files in a
>> directory called SAENG.  This is unique to DM.  I'm guessing it means
>> "Stand-Alone English files".
>> Secondly, there is a decent progression of file versions from 132 to
>> 157.  There *is* a decided jump from 109 to 132 and timestamps have them
>> separated by more than a year.  We can imagine this to be consistent
>> with your mid-70s incident, but that's a rather flimsy assumption.
>> I understand Scott Cutler was one of the people who worked on attaching
>> disks to DM, using the new Mathlab PDP-10 for testing and bringup since
>> it conveniently had the same kind of DEC disk controller.
>> Outside Dynamic Modeling we have good coverage of source files for
>> DSKDMP going all the way back to 1971 were it seems George Mitchell and
>> Fred Wright were involved with (creating?) early versions.  It seems not
>> long before that MACDMP was used to boot ITS.

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