NSSC-1 Instruction Set Came From OAO

A project log for NASA Standard Spacecraft Computer-1 (NSSC-1)

Documentation for the NSSC-1 Used on the Hubble Telescope

Dave's Dev LabDave's Dev Lab 06/22/2021 at 00:498 Comments

As noted in several documents, the NSSC-1 appears to have evolved from the earlier OAO-C and OAO-3 computer systems. As such it appears the instruction set is almost identical based on notes provided from Ann C. Merwart. Although the document with the full instruction set for the NSSC-1 appears to not be available, we do have access to the OAO-3 Instruction Set. This datasheet describes a Noun/Verb configuration similar to that of the Apollo era computers.


David Given wrote 07/04/2021 at 09:01 point

I've done the OBP simulator: The AOP is very similar, but streamlined and with some extra useful instructions. I'm now really curious to know what the NSSC-1 is like!

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Dave's Dev Lab wrote 07/04/2021 at 17:26 point

awesome! i'll check it out and add it to my reference material!

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argent.dt wrote 07/03/2021 at 01:54 point

Machine language for the DD-516 and AOP/NSSC-1 were incredibly similar to the PDP-8. Just take the RISC set and change the memory range. If you knew one, you could program the rest. If there are gaps in what you know of the instruction set then I'd suggest you look there.

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David Given wrote 07/02/2021 at 09:14 point

I've found the specs for the AOC (Advanced Onboard Computer, the successor to the OBC that the OAO-3 used): It's very similar to the OBC and fills in some of the gaps (the OAO-3 doc doesn't give the opcode encoding for NEG, for example!). A few instructions have been renamed, too (IAZ -> TEZ, for example). It's likely the NSSC-1 is similar.

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Dave's Dev Lab wrote 07/02/2021 at 15:03 point

awesome! i'll add it to my docs!

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David Given wrote 07/01/2021 at 21:43 point

Where did you get the OAO-3 document? I have about half a simulator for it done, and would really like to see the diagnostics suite for it if it's available.

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Dave's Dev Lab wrote 07/01/2021 at 21:49 point

i was able to find a good number of documents about OAO-3 (OAO-C) on the NASA public document archive. this specific document was found when i did an author search for "A. Merwarth".

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Dave's Dev Lab wrote 07/01/2021 at 21:51 point

@David Given - i've sent you an invite to join this project if you would like to contribute...

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