I have a water cooled x299 build with a 7940x on a Rampage VI Apex. Less than 2 months ago I added an Asus Dual 2080ti OC card and it has been running fine until last weekend (have not even got around to overclocking it yet).
I first noticed low performance in games. Inspecting the FPS, it looks to have been halved in some situations - running benchmarks like 3dmark gives me 8000-9000 graphics score on TimeSpy when before it would be 15000-16000. CPU score and CPU benchmarks are unchanged.
Looking at the GPU sensors, temp seems fine (sitting at low 60C), usage is fine, what is not fine is Power % - the card starts off with my set power target (110%) but within a few seconds it falls down to 50% TDP where it stays. Performance is normal for those first few seconds (high FPS) but falls off with the TDP. PerfCap from GPUz in the below screenshot shows how this is happening (Pwr reason).
Have tried changing drivers, even under-clocking the card. I have tried testing from a completely cold card (left computer off overnight, turned on and went straight into 3dmark) and exactly the same behavior happen - the common trigger seems to be when the GPU temp gets to 60C, the PerfCap: Pwr kicks in.
Help please!