Re: cpu temperature readings

[mlelstv%serpens.de@localhost (Michael van Elst)]

kre%munnari.OZ.AU@localhost (Robert Elz) writes:

>I have been running that kernel now for approaching 18 hours.   At boot
>time (when coretemp is being attached) Tjmax was read as 115 (on all cores,
>I don't know if that's supposed to be a per-core value, or not, but that
>doesn't matter), and nothing I have done since (including changing the
>cpu frequency target (and actual frequency) has made any difference, it
>seems to simply be a constant 115 no matter what (and the effort to read
>it every time it is used, rather than just remember what was read first,
>seems to be unnecessary - at least on this processor (and perhaps BIOS).

That's what I found first, the i9-12900KS (KS for the selected die)
actually has a Tjmax of 115C (but would report 100C by default, a value
that the BIOS may change).


>I have just set the cpu freq to 3401 (enabled the "turbo boost" - though
>I am not convinced there's an actual turbocharger in the CPU anywhere)
>and the temps more or less immediately rose to the low 50's (a 15 degree
>increase).   I suppose that is possible, but it seems a bit extreme, just
>for enabling higher speed on a system which is really doing nothing that
>matters.

To support the "turbo" speeds, you need higher voltages and it is plausible
that the voltages need to be set for the worst case because switching the
clock to "turbo" doesn't control the voltages (or not fast/precise enough).

That effect is usually not that noticable, but my guess is that the bias is
so much higher for the selected die.

You can probably avoid this, if you limit the chip to performance of the
non-selected die (in real applications it will probably lose 1-5%). The
BIOS should have a setting for the cTDP value that you can play with.