Systems running hot?

Dag-Erling Smørgrav des at
Tue Dec 22 12:30:59 UTC 2009

James Phillips <anti_spam256 at> writes:
> If you look at the Hardware monitoring screen in the BIOS you may
> notice the temperature readings are unitless. I don't think that is an
> accident, though they roughly correspond to Celsius temperatures.
> [...]  The reported system temperature went from 65534 -> 65535 -> 0
> -> ... -> 4 before I got bored.

Well, Those Of Us [tm] who actually read the docs and wrote the driver
know that the temperature is reported by the CPU itself as a 6-bit
number which represents degrees Celsius below the junction temperature.
I have no idea where your 65534 came from, but it certainly didn't come
from the CPU.  It may have come from an i2c probe mounted on the
motherboard, possibly somewhere near the CPU, or maybe the BIOS made it
up out of thin air, or maybe you were actually reading the clock, not
the temperature.

(FWIW, last I checked, my laptop's BIOS reported the system temperature
in degrees Celsius)

> Temperature probe in case rose from 295K -> 304K (+-1% ~ 22C -> 31 C)
> (not all measurement guaranteed to be simultaneous)

The coretemp driver reports the CPU's core temperature (as the name
suggests) which is almost always higher than the case temperature.

Dag-Erling Smørgrav - des at

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