Comment by jsheard
3 days ago
IBM PowerPC 750X apparently, which was the CPU the Power Mac G3 used back in the day. Since it's going into space it'll be one of the fancy radiation-hardened versions which probably still costs more than your car though, and they run four of them in lockstep to guard against errors.
https://www.eetimes.com/comparing-tech-used-for-apollo-artem...
> fancy radiation-hardened versions
Ha! What's special about rad-hard chips is that they're old designs. You need big geometries to survive cosmic rays, and new chips all have tiny geometries.
So there are two solutions:
1. Find a warehouse full of 20-year old chips.
2. Build a fab to produce 20-year old designs.
Both approaches are used, and both approaches are expensive. (Approach 1 is expensive because as you eventually run out of chips they become very, very valuable and you end up having to build a fab anyway.)
There's more to it than just big geometries but that's a major part of the solution.
I'm not sure what artemis or orion are, but you can blame defense contractors for this. Nobody ever got fired for hiring IBM or Lockheed, even if they deliver unimpressive results at massive cost.
Put a 4 nm CPU into something that goes to space and see how long it would take to fail.
One of the tradeoffs of radiation hardening is increased transistor size.
Cost-wise it also makes sense - it’s a specialized, certified and low-volume part.
I don't disagree that the engineering can be justified. But you don't need custom hardware to achieve radiation hardening, much less hiring fucking IBM.
And to be clear, I love power chips. I remain very bullish about the architecture. But as a taxpayer reading this shit just pisses me off. Pork-fat designed to look pro-humanity.
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