Re: cpu temperature readings

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Thu, 29 Jun 2023 20:18:31 +0200
    From:        Michael van Elst <mlelstv%serpens.de@localhost>
    Message-ID:  <ZJ3K926aTKNFXpVC%serpens.de@localhost>

  | Unless there is a BIAS on those numbers and the real values are maybe 15
  | degrees higher.

That's exactly what they were.   I added some extra debug code to
coretemp.c, to tell me what was being read as Tjmax, every time that
value changed (before it was forced to be 100 if the value read was
outside the [70,110] range).   I also changed that range to be [70,130].

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).

Currently it is running @3400 and with room temp about 30, core temps
(on a mostly idle system) are fluctuating around 40.   I have just turned
the A/C on (I have been out all day, so it was off) and the room temp is
dropping, so are the core temps, that's all fine - more around 36 at the
minute, but they will go down as the room cools more.

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.

kre