Unfortunately I never found out what was going on. It never happened again. I did upgrade to the latest BIOS. The BIOS on my Rog Strix B450-F Gaming was a few years old. I cleaned my case (almost no dust). My max temp for 2 years has been 67C at 100% utilization. Now it is 71C. I'm running a 2700X with Noctua NH-U9DX / 2 fan config. A masterbox 5 lite with the front panel removed with 3 fans in the front covered in mesh.Did you ever find anything out on this? I have just experience the same issue where it says my HTC and PROCHOT EXT (not even sure what the latter is) thermal throttled though my maximum CPU temp was 70.4C
@Martin Everything is fine but still see thermal throttling on htc this week while playing BF5. 3700x clockspeed is still around 4.2ghz. AMD 220.127.116.11b bios is still buggy atm so I am on the last 18.104.22.168 until 22.214.171.124 is stable enough for me to update bios.I'm not sure why Thermal Throttling is asserted on some systems when all temperatures are OK. On some systems this seemed to be caused by external agents like the SIO/LPC chip, which most probably did this because the chip's logic reached some invalid state. Perhaps a BIOS update might fix this.