Systems running hot?

James Phillips anti_spam256 at
Tue Dec 22 07:42:27 UTC 2009

> Date: Mon, 21 Dec 2009 13:26:26 +0100
> From: Dag-Erling Sm?rgrav <des at>
> Subject: Re: Systems running hot?
> To: Doug Barton <dougb at>
> Cc: freebsd-current at
> Message-ID: <861viosebx.fsf at>
> Content-Type: text/plain; charset=utf-8
> Doug Barton <dougb at>
> writes:
> > In the last weeks (I generally update to the latest
> HEAD daily) It
> > seems that my -current laptop is running hot
> temperature wise, even
> > when it's idle, or nearly so. The temperature sensor
> (via wmbsdbatt)
> > generally stays in the 80s C, as opposed to the 70s,
> and the fan is
> > regularly on its "medium" speed as opposed to the low
> speed.

As far as I can gather, Intel considers the relationship between sensor readings and actual temperatures a trade secret. You have to take those numbers with a grain of salt.

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.

For a DG31PR based desktop (latest (0068) BIOS revision) I recently observed a cold boot CPU temp starting at 24 and climbing to 30 before I got bored. The reported system temperature went from 65534 -> 65535 -> 0 -> ... -> 4 before I got bored. Temperature probe in case rose from 295K -> 304K (+-1% ~ 22C -> 31 C)(not all measurement guaranteed to be simultaneous)

> The maximum operating temperature for a Core 2 Duo is 75
> C.  The idle

True, but ACPI reporting 80C does not make it so.


James Phillips

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