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Large discrepancy between CPU core temps


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#1 Alchemist

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Posted 24 April 2013 - 02:18 PM

I have just purchased an Intel E8400 to upgrade a machine that was previously running an E6600. The installation was annoying because of the trouble in mounting the CPU cooler, as there always is. (If only they could think of a better way to do this!) But the new CPU works fine, with one oddity. According to the on-chip sensors, there is a full 14 C difference between the two cores at idle! This is concerning, of course. I have already tried remounting the CPU cooler (argh!) and actually changed the orienation since it is one of those "tower" coolers with heat pipes in it. I thought maybe the location of the pipes was making it cool one core much better than the other. But after a 90 degree shift the large difference between the two cores remains. There was only a few degrees difference between the cores in the E6600.

After checking the cooler very carefully, it looks properly mounted and really looks like the two cores just have different temperatures. Is this a sign of potential problems? Could the contact inside the heat spreader have been botched at manufacture? I have run a high load on the machine to see what happens, and the peak temperature isn't too bad. 53-54 C for the warmer core at nearly 100 percent load while transcoding video. The difference between the cores shrinks to about 10 C when both are at full load. So it doesn't seem to be a critical failure of the heat spreader. But the difference is still disconcerting. Are the heat sensors inside CPUs really that variable?
 

 



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#2 s1lents0ul

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Posted 24 April 2013 - 03:42 PM

3-4 degrees C seems to be the running "normal" difference for CPU cores, 10 is not really acceptable.

 

Perhaps the heatsync is not seated evenly, or the thermal paste is not good.

 

What brand thermal paste did you use, and how did you apply it?

 

Did you use a thin even layer of thermal paste, or did you put too thick of a layer on one side of theheatsync.

 

To much paste is bad.

 

To little paste is bad

 

Uneven heatsync or rough surfaced heatsync is bad.

 

The paste helps with the uneven/rough surface, but only to an extent, if your heatsync is that poorly made it may not do its job correctly.


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#3 Alchemist

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Posted 24 April 2013 - 05:13 PM

The heatsink is a CoolerMaster Hyper TX3 and it came with paste included, so I used that. I have a little plastic spreading tool, so I carefully spread the paste on the base of the heatsink before installing it. If it were a problem with the heatsink I would think that re-seating it differently would have at least changed which core had the higher temperature, or the amount of the difference. But it didn't. Same temperature difference despite the 90 degree change in orientation of the heatsink. Similarly, if the heatsink were not properly secured, I would expect to see much more problem at high load. But the cores don't overheat under heavy load. Just keep a 10 C spread. I suppose I could put the stock heatsink on and see if that makes a difference. Installing the heatsink is such a pain in the arse, though. Having to do it over and over gets very annoying.

#4 s1lents0ul

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Posted 24 April 2013 - 10:08 PM

I was looking around, it does seem that some CPU's are made and they have the difference in temp no matter what..not sure if its a defect or brand specific but there are many others out there with your same issues, it seems to be working out for them in the long run, it does not seem to be damaging as one would first assume/fear.

 

I am not as well versed as some when it comes to this subject though, perhaps someone else will have more experience and be able to help you further.


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#5 Alchemist

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Posted 25 April 2013 - 10:38 AM

Well, now I've run into something very odd indeed. I had bought two of these CPUs, because I have two almost hardware identical computers that I wanted to upgrade. When I removed the other one from the packaging today I noticed that it had a dot of something covering one of the pins on the underside. Now I don't have a lot of experience with the multi-core generation of CPUs, but I have never seen or heard of a pin being deliberately blocked on one of those. Do you have any idea how to research whether that is a legit "fix" of some sort, or a mistake/problem? It looks very precise, so it was probably done deliberately by someone.



#6 Alchemist

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Posted 25 April 2013 - 03:07 PM

Got an interesting answer to the marked CPU question, anyway. A guy who runs a local computer shop says the mark would come from a contaminated socket. Paste was apparently dropped into the socket, and a pin with the stuff on it would leave a nice neat dot where it contacted the CPU. That sounds very sloppy for Intel testing. Which means these CPUs sold as "new" most likely are not. I'll have to take it up with the vendor. After cleaning the bottom and installing it, this second one does seem to have the two core temps very close together. Within 2-3 degrees most of the time. Maybe I'll keep it anyway, but I suspect it isn't truly new.



#7 s1lents0ul

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Posted 25 April 2013 - 09:57 PM

Well, surely no one on here would have been able to know your CPU had such defects, but we are sure glad you were able to figure that out! That is amazing, and your temp difference of 2-3 celcius is much better/accepted over the 10 degree difference!

 

I do hope that you can get a replacement unit and that it works similarly to one you have now.


==]--s1lents0ul-->




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