2 ms·

So they're saying that one memory chip in the FDS has failed, representing 3% of the FDS's memory. The FDS memory seems to be CMOS, which was apparently novel

So they're saying that one memory chip in the FDS has failed, representing 3% of the FDS's memory. The FDS memory seems to be CMOS, which was apparently novel at the time of launch[0]. I suppose that means it's static RAM. I have a notion that at least some CMOS SRAM came in 8-bit wide chips, storing 1-4 Kb. So that would imply total RAM of between 20Kb and 80Kb. I haven't managed to track down many definite numbers or facts. It's programmed in FORTRAN77; it's a very long time since I was adjacent to FORTRAN, but as I recall, all variables were global. I'm sure it's tricky to write code that works even if there's a hole in physical memory; but I guess the absence of heaps and caches must help a lot. [0] https://www.allaboutcircuits.com/news/voyager-mission-anniversary-computers-command-data-attitude-control/ https://www.allaboutcircuits.com/news/voyager-mission-annive...

ItCouldBeWorse 3y ago
Couldn't you declare a variable that is mapped to the danger zone and canary it.
- AstralStorm 3y ago
  Unfortunately there's very little code space remaining to code in such a workaround. Easier and safer to rewrite the addresses in a patch.
  - denton-scratch 3y ago
    That's what I assume the process would be. In those days, a "patch" didn't mean a source-code diff; at least, not in the systems I worked on. We got binary patches. I think they were packaged for use with a program we called "patch", but you could definitely apply them with a hex editor, in a pinch. We got patches for the OS itself this way. But we didn't have access to the OS source, nor the build tools - the OS was written in a proprietary ALGOL derivative, and we didn't have the compiler. I was once shown how to patch the COBOL compiler so that you could produce programs that couldn't be written in COBOL, things like messing with IO ports.

ItCouldBeWorse 3y ago

Couldn't you declare a variable that is mapped to the danger zone and canary it.

AstralStorm 3y ago
Unfortunately there's very little code space remaining to code in such a workaround. Easier and safer to rewrite the addresses in a patch.
- denton-scratch 3y ago
  That's what I assume the process would be. In those days, a "patch" didn't mean a source-code diff; at least, not in the systems I worked on. We got binary patches. I think they were packaged for use with a program we called "patch", but you could definitely apply them with a hex editor, in a pinch. We got patches for the OS itself this way. But we didn't have access to the OS source, nor the build tools - the OS was written in a proprietary ALGOL derivative, and we didn't have the compiler. I was once shown how to patch the COBOL compiler so that you could produce programs that couldn't be written in COBOL, things like messing with IO ports.