AMD seems to have something similar enough to
hyperthreading to be wary
of. A number of the AMD CPUs shows twice as many threads as cores. I
know that they do double caching, I don't know if this is what the Linux
kernel is seeing as shadow cpus or not.
At least for their FX eight core cpus, two cores share one floating
point unit, so ever since early 80x86SX times, where you could buy a
dedicated 80x87 FPU, those are not to be considered "full" cores any
more. Though ought be complete asides the FPU, and therefore a little
more "true" than HT.
Not sure however, if that matches your idea of a shadow CPU
Happy modern times. Penis competition about virtual cores. Because it
sounds the same and is cheaper.
Thanks for the links, haven't had time yet to read them, though.