SpaceX supposedly mostly runs non-rad-hard parts, the ostensible reason being because its more cost effective to double or triple up than buy specialty equipment. Do you have a source for this?

You are conflating with their rockets. They don’t go space grade in their rockets because they don’t need to. They’re not up there for very long, and the avionics can be shielded behind large rocket stages.

Starlink satellites use space-rated AMD Versal chips: https://www.pcmag.com/news/amd-chips-are-powering-newest-sta...

Possibly, although that article seems quite confused as well (of course they need custom silicon, and of course that doesn't mean anything about what COTS parts they do or don't use). It would be nice if SpaceX would publish more about its compute architecture.

Google tested the radiation tolerance of tpus which include hbm and they performed fine. https://research.google/blog/exploring-a-space-based-scalabl...

That is not a realistic test, as any space engineer could’ve told them. First of all that’s on the very low end for a cosmic ray, an order of magnitude below the average energy. But the average energy doesn’t matter because there is a very wide distribution and the much more intensive cosmic rays do far more damage. It was also not a fully integrated test with a spacecraft, which matters because a high energy cosmic ray, striking other parts of the spacecraft, generates a shower of secondary particles that do most of the damage of a cosmic ray strike.