High (near 80C) but fluctuating core temperatures under load

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Frank46

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Dec 16, 2013
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10,510
This is my first home built system. I might be having CPU heat issues.

Case: Cooler Master 932. All the fans appear to be blowing outward.
Power: Corsair 750W.
CPU: Intel I7-4770, stock cooler. I tinted the CPU with Arctic silver before installing the cooler.
Mobo: ASUS Z87-PRO-V. TPU switch setting 2 (CPU base clock rate and ratio boost for enhanced performance. EPU enabled (intelligently moderate power consumption.)
Memory: 32G G.Skill 2133 memory
BIOS: Enabled XMP (for 2133 speed memory), Changed DIMM power from 1.500 to 1.520 because the voltage measured 1.523. Enabled virtualization technology.
OS: Ubuntu Linux
Graphics card: NONE. Using Intel graphics.

When assembling the system, I left the heat sink just sitting on the processor for about 5 minutes while frantically trying to figure out how to secure it. One word (push) is worth a thousand pictures.

At this point, the power has been cycled only about 5 times and is in its first cycle where it has been stressed to any degree.

When idle, the CPU temperature sits at around 30C. Using SETI@home for stress testing, at 100% CPU the core temperatures are all near 80C. Rolling back to 85% CPU (which is confirmed by the top command,) the temperatures are in the mid to high 70s but sometimes drop to mid 50s.

Should I be concerned with the high or fluctuating temperatures? If so, what actions should I take?

Additional note: Suspending the SETI@home processes drop the CPU load down to almost nothing and the core temperatures down to around 30c.
 
Solution
ewok93
It is possible that that fixed that. Run a stress test and see if it goes above 60, if not you're okay. I asked you to try reapplying, because sometimes they don't mix well, and the factory paste isn't usually that good, so adding dried out paste to more paste can just add more of a barrier for the heat.
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Frank46

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Dec 16, 2013
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I did not remove the pre-installed paste from the heat sink. For tinting the processor, I first cleaned the chip with isopropyl alcohol, put a small dab of arctic silver on the processor, spread it out with a piece of plastic, then cleaned off everything with a paper coffee filter paper. This tinting was done per the Arctic Silver guide, in order to fill in microscopic air spaces on the processor. It probably wasn't necessary, but I already had this paste because I had to reinstall a heat sink on another computer about two weeks ago when replacing its power supply.

I'm not sure what I need to do if the loaded temperature is too high. Do I turn off the TPU overclocking switch? Reverse some or all of the case fans? Re-apply thermal paste? Reduce DIMM voltage? or what?

The Arctic Silver guide also says that thermal paste doesn't reach full effectiveness until the processor has been cycled a few times.
 
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ewok93

ewok93

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Mar 18, 2013
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That is your problem. You reapplied paste over more paste. Remove all of it with a coffee filter and alcohol like you did before, but on the chip AND heatsink. Place a pea sized dot of paste on the chip and install the heatsink.
 
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Frank46

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Dec 16, 2013
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10,510


Just to be sure that we're on the same page: The tinting process I described only adds a microscopic film on the processor. You can easily see through it and read the processor lettering. The paste on the heat sink was new and pre-applied at the factory. It was not supposed to be removed before being used. I didn't do anything to the heat sink paste.

You are essentially saying that the microscopic tinting film I added was too much paste, right? If true, that seems to me like the amount of paste needed can't vary by more than a microgram or so.

I can easily believe that my failure to secure the heat sink immediately could have caused a problem and that I should do it over, but can't convince myself that tinting alone would botch it up unless there were some sort of paste compatibility issue.
 
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Frank46

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Dec 16, 2013
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As an experiment before pulling off the heat sink and applying only Arctic Silver, I turned off the motherboard TPU switch. Now at 100% CPU usage on 8 threads, the temperature sits near the low to mid 60c range. If you still think that I should reapply the paste, that will be the next step.

I apologize for being so reluctant to just do this, but I like to get to the why of what I'm doing. Your advice kind of implies that I should have removed the factory paste in the first place. Or maybe letting it sit for a few minutes before pressing down the connectors botched the installation. Or mixing paste types is a bad idea. Or it doesn't really matter: CPU temperature fluctuations imply a bad heat sink seal, period.
 
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ewok93

ewok93

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Mar 18, 2013
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It is possible that that fixed that. Run a stress test and see if it goes above 60, if not you're okay. I asked you to try reapplying, because sometimes they don't mix well, and the factory paste isn't usually that good, so adding dried out paste to more paste can just add more of a barrier for the heat.
 
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Solution
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Frank46

Honorable
Dec 16, 2013
5
0
10,510


OK. I removed the old thermal paste (which was pretty evenly distributed but had a splotchy look) and put on Arctic Silver. This did not have much effect. The only difference I see is that now the temperature seems to change more slowly for the last 10c both when heating up and cooling down. It still gets up to the same high temperatures at the same switch settings.

For now I'm going to leave the TPU switch off. This should keep me down to the low to mid 60s.
 
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