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Rapid CPU temperature changes - good or bad?

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December 21, 2008 1:45:24 PM

Hi everyone,

I have recently gotten involved in the World Community Grid grid computing project and am running their software on my laptop with Intel Core 2 Duo T9300 and Vista 32 bit.

I've been monitoring the CPU temperature using SpeedFan and noticed that my CPU temperature oscillates between 40 and 55 degrees Celsius. I know that this is because BOINC uses the CPU at 100% for a few hundred milliseconds out of each second. Even under a constant CPU load of about 40%, the temperature oscillates from about 45 to 55 degrees Celsius.

Should I be concerned? My concern is that the rapid heating and cooling will shorten the CPU's life because the chip will expand and shrink repeatedly.

Thanks in advance.

Regards,
William
December 25, 2008 5:34:37 PM

Having emailed Intel support, they assure me that there is nothing to worry about. I'd still like some one here to share their experiences.
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December 25, 2008 6:24:07 PM

thermal cycling isn't good for the cpu in the very long run, but 10 degrees is kinda small.... it'll probably take many many years to actually brake it...

btw if you allow BOINC to use all available cpu time, ie 100% usage at low priority of course, shouldn't that stabilize the temperature... That's the way I've been running boinc for years :) 
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December 25, 2008 6:28:14 PM

*break not brake lol (can't edit....)
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December 25, 2008 7:16:35 PM

I am not sure what you mean by low priority. If you mean letting boinc run using a low thread priority, all that will happen is that any other process wanting to use the CPU will get a chance first. That won't stop boinc from using the CPU 100% of the time if I'm just running something like word. The problem with that is my CPU temperature shoots up to 70 degrees, at which point I pause boinc and set it back to 30% CPU time.

I tried to use ThreadMaster to limit boinc to 30% CPU usage so that I could smooth out its CPU usage. ThreadMaster battled to bring boinc under control, sometimes failing to do so before the CPU temperature reached 70 - my limit.
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December 25, 2008 8:51:03 PM

yeah, that's what I meant.
is there an option in Speedfan to show distance to Tjmax? Tjmax is the temperature limit specified by Intel that the cpu should't exceed, anything below is considered 'safe'. AFAIK those laptop cpus have higher tjmax values than their desktop counterparts so 70ºC might not be so bad... btw is that core temperature or just cpu case? cores run usually 10-15ºC warmer than the case

Have you cleaned out any dust that might have gotten stuck on the heatsink lately?
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December 25, 2008 8:59:26 PM

Intel says that 105 degrees Celsius is the maximum temperature for the Core 2 Duo T9300. I just don't like to go over 70 because I want to be safe. Also, I have been quoting the core temperatures that SpeedFan reports (both of them experience the similar changes). I don't think it is reporting the CPU case's temperature.

Since the laptop is still inside warranty, I haven't cleaned out the fan. However, since its idle temperatures are around 40 degrees and the ambient temperature is about 30 degrees, I don't think there is anything wrong with the fan.
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December 29, 2008 7:19:07 PM

I've now been running BOINC at 100% for a few days. Its a bit cooler here now, so the CPU core temperatures are 65 and 62 degrees Celsius. Apart from a performance hit, nothing has crashed yet, its even complete quite a few work units. I guess the only question now is whether this does more damage than the temperature cycling?
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