We had one of our 2 host CPUs fail and it was replaced by the exact some type. The machine recognizes it but the ESXI host does not. So we not only loose 1 cpu but 1/2 of the ram.
That's a really low-level function and if it's not working, I don't think there's a whole lot we can do for you here. This is why you should have support.
that's why I reached out to the forum.