Gigabyte (I have an ax370 k7 and an 1800X with a Phanteks TC14PE cooler) seems to use a "CPU" temperature calculated in mysterious ways for fan control.
It fluctuates a ton based on different workloads and often reads below ambient. As a result, to keep my fans spinning at what I think are logical speeds (ramped down at idle, ramp up on load), my fan curve in the bios for the cpu is set to something stupid like 20% at 30C and 80% at 40C. Basically the min/max is very narrow as the temperature input used to control it is very unrealistic.
I first noticed this behavior while running IBT (linpack). Basically, I had my fan curves set to cover the more natural range of temperatures (low speed at 30, medium at 50, and max at 65 or so for my cooler), but my fans would never ramp up and the cpu would throttle to 3.5Ghz down from 3.6Ghz when Tctl reaches 72C or so.
All this time, the "CPU" temperature never shooting past 44Cish. I know about the offset built into tctl for the X cpus, but the throttling has me a bit puzzled.
Anyway, after redoing my fan profiles, at least the fan ramps up, but I still throttle to 3.5 in IBT.
I'm not really sure where I'm going with my post here but I guess I need a better cooler? Or maybe Phanteks has poor mounting pressure... I took the cooler off and paste was spread well but the contact area looked very tiny. Maybe too much of a convex surface on these coolers?
I know it cools decently, but the poor paste contact mark and the throttling combined with the mystery temperature values really has me concerned.