High core/hotspot on Eisblock Aurora Acryl RTX 4080 Strix

[kubko]

Hi,
I recently installed waterblock on 4080 Strix. I followed instructions but made one difference. On memories instead of supplied pads I used Thermal Grizzly Minus pad Advance, however they are same thickness - 1mm. All other pads on the PCB are the one supplied. What I noticed is that TG pads are pretty stiff and maybe not very compressible like the pads supplied with block.

My flowrate was about 100l/h with 25% pwm on VPP Apex pump
Water temperature did not raise over 27C

So the behavior with temperatures I've observed, higher wattage draw makes GPU's core temperature grow exponentially. For example if my GPU pulls 250-300W the temperature is around 58-65c what is slightly worse than Strix air cooled. However once my GPU gets to 350W I was seeing 70-75C (core not hotspot!) what I think is really high. What is interesting is that my memory peaked at around 45C what I think is really cool. Do you think my memory pads could cause issue with die pressure even though they are same thickness? Are here any specific pads you recommend, or should I try order some putty for memories?

I'm dumb I didn't take photo, because I tried to remount the block because I thought something was wrong with paste application or screw pressure but got same result. Couldn't evaluate paste contact on die, however on pads I could see memory chips imprinted on surface really well.

 

[Eddy]

1 mm pads are not all the same. There’s a reason ours are extremely soft. If you use harder ones, the contact pressure won’t be correct. The pads need to be able to compress down to about 0.7 mm. Their Shore hardness is 25 Shore 00. If the pads are harder than that, it’s no surprise you’re getting poor temperatures.

 

[kubko]

Didn't know there are so many variables with pads sometimes its PITA to even find correct thickness leave alone hardness, my bad.. I wanna try Honeywell HT10000 putty, that should compress perfectly on memories. Rest of the pads should be fine as those are all that came precut with the block.

Once I get to draining loop and disassemblying, I will update with photo of cooler to evaluate if I had poor contact on the die. Thanks for now!

 

[Eddy]

Putty is no problem. It’s very soft and adapts well to everything. But with pads, it’s not just the thickness that matters, the hardness is important too. For GPU coolers I would always choose pads that are as soft as possible. Hard pads are not an advantage here.

And with the RTX 3000 and RTX 4000 series, there is the added issue that GPU heights can vary a lot and often even fall outside Nvidia’s own specifications. The height differences are usually around 0.2–0.4 mm, which sounds tiny at first, but it already makes a huge difference.

That’s why soft pads are always better for GPUs. In the end, the thermal conductivity barely matters.