[mythtv-users] Out of nowhere, cpu is now cooler

Roger Heflin rogerheflin at gmail.com
Sat Jun 14 02:10:51 UTC 2008

Steve Peters - Priority Electronics wrote:
> Hello,
> I do a lot of nuvexporting of my recordings, always pushing the cpu to 100%
> for hours at a time (core 2 duo, 1.8ghz, 800mhz bus).
> Usually my cpu gets up to around 45-50 degrees Celsius. My cpu fan, the
> stock intel one, usually goes around 2000 to 2200 rpm or so when at this
> temp. This has been a constant throughout the last year or so. I check temps
> and fan speeds all the time, and they're always around this area.
> I recently switched to mythbuntu 8.04, and all of a sudden, my temps never
> go above 39 degrees celcius when at 100% cpu usage (100% on each core). The
> cpu fan, which is auto controlled by the motherboard/bios, never goes above
> 1600rpm. It's now hotter in the house than it was 6 months ago. I just don't
> get it.
> I mean, I'm not complaining.I'm even thinking of overclocking it now, but
> just don't want to mess anything up.
> But how and why could this be? I have always used mencoder to nuvexport my
> recordings, and it goes the same fps, if not more now than it ever did
> before. I get around 30-35fps transcoding with some good quality settings.
> Nothing in the system has changed in the past year except for the fact that
> I've added another drive inside it, which I'd think would raise temperatures
> if anything. Also, I have a thermometer in the cabinet that encloses the
> computer.yes, it's totally enclosed except for some vents in the back, and
> that thermometer never gets above 85 degrees F except when it's a hot day.
> Any ideas?
> -Thanks
> -Steve

There was a recent kernel change that changed the temp readings on a number of 
cpus (without the actual temp changing).

At best the sensor readings are rough guesses (the sensors are in general really 
cheap, and poorly calibrated and on a good day have an accuracy of a few degrees 
C-if everyone did *everything* right-the kernel, the MB maker, the bios version, 
and the sensors.conf file), at worse they are completely meaningless and just 
wrong.  Unless you actually measure your cpu temp and compare it to the actual 
reading, they are often wrong, so don't count on what you see being correct.

About the only ones that I have been recently trust is the ones being read 
directly off of the cpu itself as at least all of the AMD's cpus are the same. 
The sensors on the MB (most of the cpu temps) are difficult, as each MB is 
different and it all depends on how good of job the MB vendor did calibrating 
theirs, and given how bad of job they do on really important stuff, I would not 
count on the trivial non-critical stuff being correct as some of the important 
stuff is often badly screwed up.


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