Re: cpu temperature readings

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

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

>cpu0: "12th Gen Intel(R) Core(TM) i9-12900KS"

The chip apparently reports a Tjmax of 100 C (as for the non-selected chip)
but actually has a real Tjmax of 115 C.

There are two caveats:

Our driver ignores Tjmax of > 110 C (and uses 100 C as default). If the
chip would report the real value, we would ignore it.

Intel recommends that the BIOS fakes the value and configures the MSR ten
degrees lower (so you see Tjmax of 90 C).


The temperature sensor reading is relative to Tjmax.

                /*
                 * The temperature is computed by
                 * subtracting the reading by Tj(max).
                 */
                edata->value_cur = sc->sc_tjmax;
                edata->value_cur -= __SHIFTOUT(msr, MSR_THERM_STATUS_READOUT);


So it could be 15C lower than reality (if the default of 100 instead
of 115 is used) or even 25C lower if (if the Intel recommenendation
is followed).