Thermal question about 920XM

My 920XM had been running hot i had the TDP set to 75 and had the BIOS overclock at 5%. I replaced the stock thermal compound with same AS5 and my temps dropped about 3-5 degrees but my system would still thermal throttle during 3DMark Vantage, Prime95 and even sometimes during SC2 and Batman Arkham Asylum. I tinkered with my TDP setting running Prime95 after each change and found the highest i could set TDP without experiencing a thermal throttle was 68. I wanted to see if this is normal or i have some sort of issue. I have considered redoing the thermal paste again to make sure i didn't screw something up.

 

I think your issue needs further investigation. I run 80/70 TDP/TDC with a 5% BIOS OC and hit 91°C in Prime95. When you did the paste job, did you thoroughly clean both the heat sink and the CPU die with rubbing alcohol or equivalent? I prefer putting a dot of thermal paste in the center of the die and letting the heat sink spread it. This way there are no air bubbles. Your fan goes full blast and hot air is coming out the rear-center of your laptop? Did you by any chance remove the thermal pad that is right below the CPU heat sink? Is the bottom or rear of your laptop obstructed? Is your ambient room temperature abnormally high? Did you turn up the vcore voltage of the CPU in your BIOS? Sorry for the barrage of questions, but we might as well start at the beginning.

 

I cleaned the cpu/heatsink with alcohol, i spread the thermal paste to get a piece of paper thickness of paste on the processor. Around the processor die underneath the plastic dell covered the rest of the process with was thermal paste dell had applied. i left it in place should i have removed that as well? i verified the fans are going fine and air is moving through normally no dust blockages. I left the thermal pads alone and room temperature is 70 degrees. I did not touch voltage in the BIOS.

 

I'm no expert, but from what I've read elsewhere, I think you might need a thicker layer of thermal paste. Correct me if I'm wrong, please!

 

Try this and see if it helps:
http://forum.notebookreview.com/alienware-m17x/530618-new-i7-940xm-es-installed-4.html#post6880976

 

try the rice grain method instead of the spread method for doing the paste that may help a bit more.

 

Well, you're sort of wrong. You can squirt the whole tube (please don't really do this) on the CPU die, and once you install and tighten the heat sink, all but what is needed will squeeze out the sides. All the paste does is fill tiny imperfections in the mating surfaces. In an ideal world, you'd have two perfectly flat and mirror-finished surfaces, and wouldn't need any TIM.

To the OP, when you took the heat sink back off, was there paste covering the whole core? If not, then you do need to apply a bit more. If yes, then I would start looking at other possible problems.

 

I just finished reapplying AS5 again. This time i made sure to clean up the Dell thermal paste that was around the die under the plastic that i had left alone last time and did through cleaning of the entire CPU. My max temp has dropped about 6 degrees on first boot with no time for the paste to burn in. I still have 2 questions, is it normal for 1 core to be hotter when under load then the others. My core 2 under load is usually about 5-8 degrees warmer then the other 3 cores when under load. This has been true from original dell paste to my 2 re pastes. Also right now i still have my system set at 68TDP/62TDC, when benchmarking with Prime95 i hit 90 degrees on my warmest core. Should i wait for the burn in to complete to start raising the TDP/TDC or can i start pushing it up now?

 

Under normal use, not all cores are equally loaded so the heavier loaded core(s) will be slightly hotter than other(s). Now, if you run something like Prime95, all 4 cores should be equally loaded and should be very close in temperature. Look back a few posts under my user name and see what I think can help with CPU temperature.
As I mentioned before, I have the 940 XM (CPU from Dell so it may differ) running Prime95 with 5% OC in the BIOS and the maximum temperatures are between 74 and 77 F. I also used AS5.