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Water Cooled GPU's in SLI. One temp 11C hotter than the other.

post #1 of 9
Thread Starter 
Just installed bitspower water blocks for EVGA 980ti Kingpin GPU in SLI.

http://www.bitspower.com.tw/index.php?main_page=product_info&cPath=173_268_270_277&products_id=3893

There is a PDF manual for the waterblock on the linked webpage if anyone wants to look at it. The manual has drawings which will help visualize the issue.

One GPU is 11C hotter than the other, 39C vs 28C at idle. When I installed the block on this CPU I checked the contact patch after applying TIM and noticed that half the GPU processor was not making good contact with the block. I thought I had addressed this by putting a little more TIM on the naked spot, I know that is stupid and that TIM is not supposed to be a good conductor of heat. I am pretty sure the poor contact patch is the cause of the problem.

My question is how to address this the best way. I am using the EVGA backplate instead of the Bitspower backplate. The screws are tightened down. I used EVGA screws because the Bitspower screws are too long to seat the EVGA backplate. The EVGA backplate is thinner than the Bitspower backplate and Bitspower screws are much longer than EVGA. The waterblock kit came with several 2.5mm thermal pads to put between the PCB and the backplate. I did not put these on. One was supposed to go underneath the GPU processor. Maybe those pads were included to press the intended areas against the contact surface. Taking the backplate off and adding the thermal pads is the only thing I can think to do. Might try to purchase screws that are about 2-3mm shorter than the Bitspower screws. Short of going with EKWB. Does anyone else have ideas?

Thanks for reading and responding.
Edited by HooDooMan - 10/20/15 at 11:27am
post #2 of 9
The lack of installed pads could be an issue. It would be worth chasing down.

Are your cards in the correct PCIE slots? Is one card in a 16x slot and the other in an 8x slot? Are both cards running at the same speed or is one running at 8x and one at 16x? It should not affect temp at idle but it’s worth checking out. I chased a problem like this on my last WC build. When I set the cards to 8x it reduced the temp difference but did not eliminate it. The cards always ran a few degrees different. I contributed this to one card getting slightly hotter water that the other. My cards where run in series.
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post #3 of 9
ok for me, I have found thermal pads to be a bad idea in any situation. I have evga blocks on my GTX580's and I have removed all the thermal pads from the cards and only use arctic silver 5.
ok so if I understand what you have done you applied thermal compound found that it was not cooling correct pulled the block away from the card and added more thermal compound to the area that had to little and reattached the card to the block
if this is correct, this is the issue, you cant do that, it never works, you will need to remove the block from the card clean all the thermal compound away from the card, and the block, then reapply new thermal compound to the whole card, then reattach the card to the block and that will fix this issue, I hope this helps.
post #4 of 9

Here is a video I made with a ek water block and keeping your backplate. Might have to do something similar with the block you got.

 

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post #5 of 9
Thread Starter 
Quote:
Originally Posted by apw63 View Post

The lack of installed pads could be an issue. It would be worth chasing down.

Are your cards in the correct PCIE slots? Is one card in a 16x slot and the other in an 8x slot? Are both cards running at the same speed or is one running at 8x and one at 16x? It should not affect temp at idle but it’s worth checking out. I chased a problem like this on my last WC build. When I set the cards to 8x it reduced the temp difference but did not eliminate it. The cards always ran a few degrees different. I contributed this to one card getting slightly hotter water that the other. My cards where run in series.

The Kingpin cards were in my system on air for a month prior to adding the waterblocks. Temperatures were always within 1-2C during this period.
post #6 of 9
I realize any of this is quite a bit of work, but you could:

- Swap the waterblocks and see if the issue is following a particular waterblock or a card.
- Try each of the cards in a single configuration. That actually can possibly be done without disassembling the loop, or you can physically keep one card only to be sure.

Also consider possible uneven load which is not unusual in SLI mode. You can disable SLI and use e.g. Furmark or any compute task to load the cards. GPGPU does not use SLI and is able to generate equal load on both cards.

I have quad-GPU setup for CUDA compute and twice in a row I have had one of the cards' temperature creeping up by +10 C after a few months of use. Disassembling that card revealed dry thermal paste, and reapplying it fixed the issue for a while. Now the thing is, I swapped waterblocks at some point, and the issue reoccurred following one specific waterblock! I replaced it and temperature is even so far, withing 1-2 C on all 4 cards under balanced load.
post #7 of 9
Thread Starter 
I disabled SLI a week ago. The load temps of the first card are lower than the idle temps of the second card. I will take the block off the second card and reapply TIM and try some other tweaks. If that doesn't work I will switch to EK water blocks.
post #8 of 9
If you can swap the blocks between cards and the problem is with one block then I would ask for an rma from wherever you bought it.

If the problem is just with how it's mounted then a careful remount with the correct hardware should sort it.
post #9 of 9
If you can clearly see that the block is not making proper contact and you screwed everything in fine then you should return it. It's not machined correctly and no ammount of thermal paste will help you "fill that gap". A shim might give you better chances.

I would return the block and get another one since the fist one is working fine, all of them being from bitspower I assume.
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