3 ms·

This isn't about a Cray, but it's roughly contemporaneous. According to https://trs.jpl.nasa.gov/handle/2014/26062 https://trs.jpl.nasa.gov/handle/2014/26062,

by ardy42 6y ago

This isn't about a Cray, but it's roughly contemporaneous. According to https://trs.jpl.nasa.gov/handle/2014/26062 https://trs.jpl.nasa.gov/handle/2014/26062, the Cassini space probe had an "SSD," and the contract to build it was awarded in 1992. It sounds like it was pretty much a RAM disk made from DRAM. I'd imagine it would be practical to build and use something similar for a multi-million dollar supercomputer where cost is secondary to performance.

walrus01 6y ago
I have also seen mention of this in spacecraft design discussion. The concept being that for things which are powered from a radioisotope thermoelectric generator, it's safe to treat the RAM as storage. Because there's absolutely no scenario after launch, in which the constant trickle of wattage flow from the RTG to the onboard DC distribution buses and computers would ever be interrupted. If the power from the RTG were to ever be cut off it would be a catastrophic mission failure anyways, entirely aside from the power to the onboard computing systems being interrupted.
- jandrese 6y ago
  Presumably the OS would be in some nonvolatile medium and the SSD would only be used for stuff like storing sensor data anyway. In the event of corruption or a system restart you would lose all of your working data but could bootstrap the system again.
  - ardy42 6y ago
    While it would make sense to have recovery routines in some nonvolatile memory to handle a system corruption use case, I'm not sure it if would be necessary for a system restart. IIRC, core-based systems had nonvolatile RAM, and I think at least some of them would continue to execute the same memory image after reset. I think the point of the GP was that one of these DRAM based recorders is basically nonvolatile for all intents in purposes in this application.
- heavenlyblue 6y ago
  > I have also seen mention of this in spacecraft design discussion. The concept being that for things which are powered from a radioisotope thermoelectric generator, it's safe to treat the RAM as storage. I don't buy it. They specifically design these systems with duplication in nature in case RAM gets corrupted by radiation in space. So you can't treat it as storage, but for very different reasons.
deleted 6y ago
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by ardy42 6y ago

walrus01 6y ago

I have also seen mention of this in spacecraft design discussion. The concept being that for things which are powered from a radioisotope thermoelectric generator, it's safe to treat the RAM as storage. Because there's absolutely no scenario after launch, in which the constant trickle of wattage flow from the RTG to the onboard DC distribution buses and computers would ever be interrupted. If the power from the RTG were to ever be cut off it would be a catastrophic mission failure anyways, entirely aside from the power to the onboard computing systems being interrupted.

jandrese 6y ago
Presumably the OS would be in some nonvolatile medium and the SSD would only be used for stuff like storing sensor data anyway. In the event of corruption or a system restart you would lose all of your working data but could bootstrap the system again.
- ardy42 6y ago
  While it would make sense to have recovery routines in some nonvolatile memory to handle a system corruption use case, I'm not sure it if would be necessary for a system restart. IIRC, core-based systems had nonvolatile RAM, and I think at least some of them would continue to execute the same memory image after reset. I think the point of the GP was that one of these DRAM based recorders is basically nonvolatile for all intents in purposes in this application.
heavenlyblue 6y ago
> I have also seen mention of this in spacecraft design discussion. The concept being that for things which are powered from a radioisotope thermoelectric generator, it's safe to treat the RAM as storage. I don't buy it. They specifically design these systems with duplication in nature in case RAM gets corrupted by radiation in space. So you can't treat it as storage, but for very different reasons.

deleted 6y ago

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