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Not that I'm skillful enough to make an emulator, but I've tried years ago to find technical documents on the Honeywell HDC-402 used in Voyager and Viking (it's
by bilegeek 3y ago
Not that I'm skillful enough to make an emulator, but I've tried years ago to find technical documents on the Honeywell HDC-402 used in Voyager and Viking (it's also apparently not related to the DDP-516 or 316 AFAIK.) There's SOME information[1], but not enough to make an emulator from what I've found.
Aside from the lack of schematics or listings, there was the problem of the assembler being incomplete!
"One problem Lander software developers had was that no adequate
assembler was ever written for the computer, perhaps because of the
changing nature of the instruction set.(110) Patches had to be hand-coded
in octal, with many jumps to unused memory space because of the lack
of an assembler with relocatable addressing." p.174 on Viking, which used the same computer
[1]https://ntrs.nasa.gov/api/citations/19880069935/downloads/19880069935_Optimized.pdf https://ntrs.nasa.gov/api/citations/19880069935/downloads/19... (page 174 onwards)
- makomk 3y agoAs far as I can tell the HDC-402 wasn't even the Viking computer that got reused on Voyager anyway - it was something NASA developed in-house from the orbiter side of the Viking mission and that presumably has even less documentation available.
- bilegeek 3y agoYou're confusing the 24-bit HDC-402 on the lander with the custom 18-bit computer on the orbiter (p.164), which had it's origins in the sequencer for the Mariner missions (p.152-154). Though given the apparent level of NASA involvement in the 402's design, and the lack of evidence I can find for use outside of NASA, it might as well be called custom.