“AMS produces far too much data to beam down to Earth, so it must carry an onboard supercomputer with 650 CPUs to do the number crunching in orbit. Partly because of this giant computer, AMS requires 2.5 kilowatts of power — far more than a normal satellite’s solar panels can provide, but well within the space station’s 100 kilowatt power supply.”
But yeah, at a profile of maybe 1W per core (I presume the interconnects, IO and storage uses a good chunk of the total power), they have to be using DSPs or an embedded core like the MIPS core SiCortex were using or the PPC 440 IBM used in the first Blue Gene/L machines.
And they need it radiation hardened. Stray high energy photons and other particles are not allowed to damage the integrated circuitry (computation errors may happen, but that can be caught by other means, e.g. redundant computation).
I seriously doubt one could crank out a hardened design of the nVidia GPU cores easily. And if so… how would that affect clock speed and die size?