I use this all day everyday 64 bit Intel, Nvidia it utilizes memory more than CPU(I have no reason to believe AMD would have any issues),, I have PhysX dedicated to the video, and have built rockets with 1k plus parts.
have you temp probed your North bridge chip, As this is can be a heating symptom (no log reports this), [as components struggle to function especially as time goes by]. also I would test my HD but this is much less likely yet possible.( assuming you have validated the files thru steam)if all that is fine, is anti virus running?
(I know you said all other things but many of them still have stuff running as system functions//windows defender)
Hope this helps
Jammer