Detecting CPU throttling on over temperature

Ian Smith smithi at
Tue Sep 8 18:09:15 UTC 2009

On Tue, 8 Sep 2009, Henrik Friedrichsen wrote:
 > I don't know whether there is a more convenient way, but you could
 > definitely check the current CPU frequency to detect whether it
 > changed from the previous one or not. There are several ways to this,
 > depends on the CPU. You can try messing with cpufreq(4).
 > On Tue, Sep 8, 2009 at 2:39 PM, Daniel O'Connor<doconnor at> wrote:
 > > Hi,
 > > I recently discovered a system where the floppy drive cable was
 > > intermittently fouling the CPU fan - I believe this caused the CPU to
 > > overheat and then get throttled by the BIOS.
 > >
 > > Does anyone know if it is possible to determine if this is the case? ie
 > > is there a way to be informed if throttling has occurred?

Might be easier to hack powerd.c as an existing pretty lightweight way 
of monitoring CPU freq (to log or signal on detected freq lowered by 
throttling, say?) even if you don't need/want it to actually vary freq 
according to load, eg setting idle/busy shift factors to 'never/always'?

cheers, Ian

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