[SOLVED] BIOS temp source? ASRock z170 extreme 7+

Nov 9, 2021
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Motherboard:
ASRock z170 extreme 7+
BIOS version: 7.60 (~2018)
Intel i7 6700k CPU OC'd to 4.4Ghz.

I was given this mobo and have just installed an AIO water cooler. The BIOS reports temperature at over 54C at idle, so I thought my thermal pasting might be rubbish. But various monitoring tools in Windows 10 and Linux Mint reported CPU core temps between 25C-30C (idle) and 63C (at 100% load- prime95). As there was no CPU throttling at 100% loading I assume that the 63C max for cores is probably correct.

So in Linux I ran sensor-detect and it found (among) other things)"pch_skylake-virtual-0", which has the same temp as BIOS reports on the main screen.

MY QUESTION:
Does that mean the BIOS temp is only reporting PCH temp?? (which would explain why it's relatively constant and higher compared to reported core temps). If so, why would ASRock choose that temp variable as representative of CPU temps and the only temp BIOS reports to the user?

My only other hypothesis is that sensor-detect found the port above-mentioned in PCH, in which case, what value is it reporting?
At this point I have given up worrying about repasting. Did it three times with same result, and PC works just fine in my use case. I would just really like to understand where/what that BIOS temp value is really referring to on this ASRock Z170 Extreme 7+ mobo.
 
Solution
bios dosnt read cpu cores, mainboard has its own sensor under/nearby cpu socket
here some random picture from internet
notice that red area which is not cooled by aio
flir_20190906T112336_575px.jpg
In the UEFI the CPU is NOT idle, it is running in a diagnostic mode that puts some stress on the CPU. Temps in the UEFI should never be considered an idle baseline. The temps registered during idle from within the OS are the only ones that matter

Thanks for the comment, I didn't know that, but given CPU core temps reported in general use -browsing, video etc are in the low 30'sC, I would think 53-54C in BIOS would be fairly thrashing it and fans are still fairly silent in BIOS.