Detecting CPU throttling on over temperature

Daniel O'Connor doconnor at
Thu Sep 10 02:48:10 UTC 2009

On Wed, 9 Sep 2009, Alexander Motin wrote:
> > around 100C.  I did pull the c2d cpu docs at one point trying to
> > look at cpufreq.  If you are bored, you can grab the docs from
> > intel and double check.
> AFAIR C2D supports three protection technologies. When CPU is hot, it
> starts reducing frequency (multiplier) and voltage, alike to IEST. If
> it is insufficient, it starts to skip core cycles, alike to TCC. If
> it is still insufficient and temperature rises above about 100C,
> emergency shutdown happens.

Hmm, I have since realised it's an E2140 which doesn't have Core2Duo 
branding (I don't know if it really IS one or not).

On the bench here I could not observe an effect by running 
dd if=/dev/zero bs=128k count=5000| md5
in a loop and checking the frequency with

However the idle time seemed to go up, but only to 10% or so, it was 
quite odd..

Still, now I have been reminded of coretemp I can monitor it 
on "suspect" systems :)

Daniel O'Connor software and network engineer
for Genesis Software -
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
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