Temp Difference Between Cores

[BlearyCzech]

I'm using the Thermalright Ultra-120 Extreme with a Yate Loon fan (47 cfm), on top of a q6600. Cores 1 and 2 are 5 degrees hotter during idle than cores 3 and 4 according to CoreTemp (32 vs 27). Now I've been running prime95 for a while and at load, there is a 10 degree difference (50 vs 40). Is this normal and if not, what could cause this? This was my first time ever seating a processor, maybe I did something wrong with the thermal grease... Nothing has been overclocked yet, this was just a baseline observation.

[wevsspot]

There will always be a difference in temperature between the four cores. The delta between all four = YMMV

 

Things to consider though if the difference seems consequential;

 

Heatsink mating surface flatness

Processor IHS mating surface flatness

Proper application of TIM during heatsink installation

Amount of retention pressure (or lack thereof) between the IHS and Heatsink

And Intel can even mess up the TIM application between the cores and the IHS

 

The first thing I always do before installing a new processor and heatsink is check the flatness on both the processor IHS and the heatsink I'll be installing. You can use a metal engineers ruler or even a utility knife razorblade. If either surface is concave or convex you might consider lapping one or both to ensure that both surfaces are as flat as possible.

[radodrill]

It's very common to see temp differences between the cores; generally on quads there there will be 2 pairs oc cores with similar temps on that pair but different from the other pair, this is due to there being 2 native dual-core chips in 1 package to comprise the the 4 cores.

[BlearyCzech]

I just checked the thermalright again and the retention pressure does not seem to be that good. I can move the heatsink up and down a little, and when I more it up there is an immediate 2 degree drop in temperature for cores 1 and 2. Do you have any recommendations on how to increase retention pressure?

 

Edit: Ran Prime95 again, with added pressure from myself, temps dropped to 40 for all cores. My mobo seems to be concave where the cpu is, causing the cpu to be lower than expected compared to the attachment points for the thermalright. Does anyone know how to fix this, or at least work around it? Maybe little plastic spacers where the backplate for the heatsink attaches? Any other ideas?

Edited May 20, 2008 by BlearyCzech

[wevsspot]

I'm not familiar with your particular cpu heatsink so this may or may not work.

 

If you are using the stock heatsink retention mechanism you might consider changing over to a bolt through design (i.e. remove the stock heatsink retention bracket completely) and go with the bolt through installation method instead. That will usually allow you to tension each individual stud to the proper torque and help alleviate any bending, concavity or convex conditions that might be affecting your total contact surface.

 

Here is a typical bolt through installation to try and explain what I mean;

 

 

This is on DFI NF4 Ultra-D and ThermalTake BT.

[Waco]

I agree, moving to a bolt down mechanism is probably the next step.

 

I modded my XP-120 to bolt down (since I removed the IHS on my Opteron) and not only is the heatsink much more secure I'm pretty much guaranteed to have the best possible contact to transfer heat.

[EllisD]

Check out this "mod": Linkage (2nd pic)

 

Seems to do wonders though i do not have any personal experience.

[BlearyCzech]

Thanks for all of the suggestions. I tried the 'washer' mod, but it still didn't seem to give me even pressure. I eventually settled with adding 2 washers to each screw just below the spring, so the spring would compress more and apply more pressure. So far its working, but I may try bolting it down if temps become an issue with overclocking... Currently at 3.6 with 55 load temps (unstable, but working on it!).

[Boanerges]

i understand that cores in the core 2 quad work in pairs and temps wil vary between pairs. i've contacted intel and they told me not to worry about core temps and only look at the cpu temps! and only gave me cpu temp limits! i could'nt believe the rudeness of there tech support telling me i don't need to know something about there product that i spent several hundred dollors on and just be concerned with what they want me to be concerned with!! like some brain washed automaton. can someone please tell me the temp limits for the cores in a core 2 quad Q6600 SLACR @ 2.4Ghz and stock fan & heatsink. Mahalo Nui Loa & Aloha

[Waco]

i could'nt believe the rudeness of there tech support telling me i don't need to know something about there product that i spent several hundred dollors on and just be concerned with what they want me to be concerned with!!

That's like getting mad at nVidia for not caring when you complain about your GPU hitting 80 C. It's not something to be concerned about.

[Boanerges]

That's like getting mad at nVidia for not caring when you complain about your GPU hitting 80 C. It's not something to be concerned about.

when i contacted nvidia about a hot vid card they told me that vid cards run "very warm" is how they put it. mine runs 118F idle. 125F under load. it's a xfx nvidia 9600gt..hope that helps waco. Aloha

[Branjo]

It also could be that the TRUE 120's base is said to not be actually flat. I have seen a few for sale on the net that for a little extra they will lap it for you, like usually 20 bucks extra.

I get strange readings from my cores depending on how much voltage I give the CPU. @ stock 1.26v my core 1 is the hottest, @ 1.33v core 2 is the hottest and over 1.4v core 4 is the hottest. For some reason core 3 is always the coolest. 10 degrees difference though would cause me a little concern, just to be sure I would remove the TRUE and check what the spread is like of the paste. There is a fine line between too little and too much. If you don't want to lap it then I would ask for a replacement, maybe yours is more convex than the rest. I really don't see why this caliber of heatsink would cater for concave CPU's when all we want is a super flat surface for best heat dissipation. Your problem could very well be due to lack of pressure but the last thing you want to do is kill a $200+ CPU for a $50+ heatsink.

 

Temp limits depend on the stepping,