How to find real CPU temperature?

[Mel Flynn]

On Wednesday 05 August 2009 04:04:18 Erik Norgaard wrote:
> Unga wrote:
> > Here is what it show on my computer:
> >
> > sysctl -a | grep hw.acpi.thermal
> > hw.acpi.thermal.min_runtime: 0
> > hw.acpi.thermal.polling_rate: 10
> > hw.acpi.thermal.user_override: 0
> > hw.acpi.thermal.tz0.temperature: 19.0C
> > hw.acpi.thermal.tz0.active: -1
> > hw.acpi.thermal.tz0.passive_cooling: 1
> > hw.acpi.thermal.tz0.thermal_flags: 0
> > hw.acpi.thermal.tz0._PSV: 90.0C
> > hw.acpi.thermal.tz0._HOT: -1
> > hw.acpi.thermal.tz0._CRT: 90.0C
> > hw.acpi.thermal.tz0._ACx: 90.0C -1 -1 -1 -1 -1 -1 -1 -1 -1
> > hw.acpi.thermal.tz0._TC1: 4
> > hw.acpi.thermal.tz0._TC2: 3
> > hw.acpi.thermal.tz0._TSP: 60
> >
> > so which is the CPU temperature, 19.0C or 90.0C? Where does it documented
> > what hw.acpi.thermal.tz0.temperature means?
>
>  From that it appears the kernel can't read the temperature sensor, this
> may be a problem with the ACPI not being properly supported for your
> processor.
>
> The 90.0C entries are different entries that take action against
> overheating, if the temperature reaches 90 putting your system to sleep
> or throtling down speed.

_PSV = throttle down CPU speed
_CRT = critical shutdown temperature

Given that these are the same value, this indeed looks like ACPI problems. 
These values should be different, and can be quite a few degrees apart, so 
that the passive cooling actually has some time to do it's work.

The acpi_thermal(4) man page details all the values. One can also use sysctl -
d hw.acpi.thermal.tz0.passive_cooling to get a short description.

If you want these values to make more sense, you should take the issue up with 
the acpi mailing list and be ready to do some debugging. At minimum you should 
provide the info outlined here:
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/acpi-debug.html
-- 
Mel