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Comment by mLuby | Hacker News Reader

Wonder if the power display computer might be susceptible to Meltdown, Spectre or Rowhammer? Or is it not programmable in the sense that everything is hardwired…

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Not susceptible to the first two because these are almost universally large-process in-order CPUs. But generally "not programmable" in the sense of being hard-wired, or just not having a way of doing remote code execution to perform the update. These systems are _really_ simple.

Why would it matter? It's not like it's running any untrusted code.

I believe the suggestion was that NASA could update the main computer with their own 'untrusted' to exploit the flaw in the power system, side stepping their own protections. But as mentioned below in other comments, these vulns are likely not present on this hardware

That doesn't make sense to me, aren't we talking about two different pieces of hardware talking together? If they could reflash the "display computer" then the problem would be solved if I understand correctly.

Even if it's really two "applications" running on the same CPU I don't see how spectre/meltdown would help since it's all about getting read-only access to "forbidden" memory. Clearly they don't need that (they know full well what's in memory), they want to be able to modify it.

In such a situation RowHammer might be used to modify the state of an other program sharing the same RAM in the right conditions but if there's one piece of hardware I expect to be hardened against spurious bitflips it's a space probe. We're talking about radiation-hardened ECC-protected RAM after all.

CPUs used in space are usually much simpler and slower than ours – they put enormous amount of resources on error correction due to radiation levels.

I suspect the CPU in this satellite is a BAE Systems RAD6000, commonly used in NASA spacecrafts. It’s extremely expensive and also brittle due to the materials used. Very hard to get due to export regulations. I tried to source one of these CPU’s outside US once.

Wikipedia at least confirms that.

Do you mean brittle in the physical sense, like a potato chip? That's surprising; I assumed that a launch subjects all components to a fair bit of shaking around, not to mention the steday G forces.

If that's the case, it looks like the chip has a surprisingly modern feature set. For example, based on this article[1], the RSC on which the RAD6000 was based had an on-chip memory controller in 1992.

It also had a branch predictor, however, this line is notable:

> Note that the RSC never speculatively executes prefetched instructions.

This means that the branch predictor only did fetch/decode, and so the chip would not have been susceptible to Spectre, as the pipeline would have been flushed and the correct instructions reloaded as soon as the condition evaluated false, before the branch would have been actually executed.

[1]https://web.archive.org/web/20131004213712/http://zmoore.net...

Meanwhile, in February 2000, at the Intel Developer's Forum, Intel demonstrates an upcoming 32-bit processor, code-named Willamette, running at 1.5 GHz.

That was the Pentium 4 not yet in existence so there is no chance of there being an x86 able to be 'Meltdowned' in space. However you are most definitely thinking along the right lines, but I am sure the NASA boffins would have tried all the hacks they could back in 2007. Or maybe the management made sure this was not possible, much like how the Voyager missions were not supposed to go beyond Saturn yet behind the backs on management everyone made sure those spacecraft could get past the edge of the heliosphere.

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