Poor cooling with Megahalems rev B?

Hi, I've just finished building my new rig and have been trying to overclock it to 4.0Ghz (with HT enabled) but am having some trouble with high temperatures.

The main components of the machine are:
i7 970 (Rev B1, not sure if that makes much difference)
Asus Rampage III Extreme
12GB Corsair XMS3 DDR3-1600 ram
Megahalems rev.b cooler with a Coolermaster Excalibur for push and Fractal Design Silent series for pull

I'm currently running at
Vcore 1.3V
QPI/DRAM (or Vtt as some people know it) 1.28

I'm testing stability using OCCT's linpack stress test and am seeing temperatures in Real Temp / Core Temp as high as 92C on two of the cores.

The question I'm really asking is whether this is reasonable performance from the Megahalems? I've already tried reseating the cooler + reapplying the thermal paste (Arctic MX-3) using the different techniques (rice sized blob and thin vertical line) but this hasn't made any difference.

Thanks in advance!

Could be many things. Bad airflow, fans aren't pushing enough air(low static pressure), or a hot chip. You have HT on and that does add a bit of heat, especially when overclocking. Also, you never mentioned ambient temps.

Ambient temp is probably around 20C, putting my hand behind the pull fan there is noticeable air flow.

Here's the layout of the case:

two thing occur immedately to me after taking a look.

Check the HS and CPU for flatness or just go ahead and lapp them.

Those two video cards (and power supply) suck up and blow out the back anything the lower front fan (if there is one, cant see) pulls in. A bay cooler in the top bays would shoot cool air directly into the cpu fans and would likely drop temps 5C.

The HS will not be flat, it will be slightly convex. Don't lap the megahalems! It's machined specifically to be convex to put more pressure over the core. Instead, lap your CPU. When I got my I7 860, it was so comically convex that I loaded in the 80s under stock settings. After I lapped it flat (took 4 hours... lol), my temps literally dropped 20c under load.

So more surface area contact between the HS and IHS is a bad thing ?

I have to say, i'm a little hesitant to lap the processor :\ Is it really the only solution?

I have also read not to lap the megahalems.

darkip said:

I have to say, i'm a little hesitant to lap the processor :\ Is it really the only solution?

I have also read not to lap the megahalems.

Click to expand...

If you have any inkling of hesitation don't do it. It voids the warranty and never lap anything you aren't prepared to lose. There are tons of tutorials online and on youtube showing how to do it. I did it once on a chip that was a hand me down and didn't really cared if I destroyed it. I would not dream to do it on a brand new chip and on my limited budget

That's an awfully expensive CPU to learn how to lap with. I wouldn't do it if I were you.

Don't worry, I certainly won't be lapping it!

I replaced the slower pull and exhaust fans with Cooler Master Excaliburs and used the slower fans for intake and now I see a max core temperature of 80C!

I also tried to tidy the cables a little:

heyya, don't forget...linpack is the most current heavy test & can burn out PWM's so 92c isn't surprising, even with excellent air cooling...I don't mess with linpack because I won't be doing anything that intensive...

One thing I would suggest make sure you are using the thermal paste that came with the
Megahalems rev B. I have read several reviews that stated you should use it. It is designed for this HS. I have a I7 950 @ 4.2G and running OCCT for an hour the temp never goes above 73C. I used (2) 1600RPM 120MM fans in a push\pull configuration. I had a Zalman 9900led and OCCT would hit 90c in less than 2 minutes so I replaced it with the Megahalems rev B and life is good.