Thermal paste on GPU suitable?

Collywobbles

Collywobbles

Collywobbles

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Joined
22 Sep 2025
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Location
Devon, England
Hi all,

I have set up a water cooling loop on my rx6800 xt nitro graphics card, and at idle the heats are really good, including that of the hot spot, as soon as I put a load on the gpu though the temps rise quickly and the hotspot gets over 110 then shuts off pc (after a couple of minutes), the delta is over 40degrees between the global and hotspot temps, this tells me that there isn’t great contact with the water block, I have tried re-applying thermal paste, last method with a thin layer spread over the whole die, exactly the same issue, I am not wondering if it’s a compatibility issue with the water block and the card, maybe the die is a different size than the water block?, anyone had any experience of this and know a fix (do I need a copper shim or even a thermal pad instead of paste).

Spec is Sapphire Radeon rx6800 XT Nitro+ graphics
Water block is

Barrow AMD Radeon 6800 / 6900XT AMD, Saphire, MSI Founders Edition Graphics Card Waterblock​


Thanks in advance.
 
It could very well be the thickness of the memory and VRM thermal pads.

Had the same issue with an Alphacool block on my RTX 4080 and it was for that reason.
 
Not all thermal pastes work well with GPUs - sometimes you need a fairly viscous paste spread relatively thickly to get good cooling performance.
 
Usually too thick so it prevents the block having good contact with the core. A solution would be to go with a very soft pad such as Arctic's TP3 pads which compress very easily. What was the contact patch on the core like? If it's good then it would have to be the VRM or memory pads are too thin and not making contact. Are you monitoring memory and core temps, if so what are they like before the shut down?
 
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