Hi John. Thanks for the advice. I have already contacted AMD Online Support. However, they're taking long to respond so I posted my query here to see if any users are familiar with problem or could offer a solution. It is proving to be a baffling one to me, to be honest. I've checked that my BIOS settings are not set to control only "1 CCD" (the only other option is "Auto", which I've set it to), but that hasn't made a difference.
I am indeed running a new copy of W10 (see my system specs below).
Is there anything I am missing or that you can think of that could be causing the problem? That is, other than what I suspect: my 3950X chipset is defective, with only one die (CCD0) working; in which case, an RMA is in order.