That’s not an issue limited to just 3080s or 3900Xs. I have the same problem with my i5-10600K and 2070 Super.
The issue seems to be that not only is the “MainThread” limited to a single core, it’s limited to a single thread on a single core. In my case that’s the 2nd thread (hyperthreaded threads don’t have as much oomph as primary threads) on my weakest core. In fact to help with this SINGLE problem, I just re-enabled my CPU OC which I had disabled due to instabilities. But there’s been a firmware update and many driver updates since then, so hopefully it sticks.
But that’s a workaround, not a fix, and even if it works I can’t imagine it buying me much. My next steps will be disabling hyperthreading on that one core, and then on all cores if it just moves to another T2 to see if that might help, too.
MS/Asobo needs to get that process spread amongst several cores, and preferably the first thread on those cores to really fix the problem. And they need to do it yesterday.
Please upvote this bug report, and hopefully they’ll read what I’ve learned, but I’d bet they already know it.
PP, ASEL, IA