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I put bitspower waterblock on my 3080 and max memory temp ive seen is 96c
 

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Gigabyte Gaming OC 3080 with a Arctic Accelero IV backplate + 3mm Arctic blue thermal pads. Core is cooled by Coollaboratory Liquid Ultra.

+120 core @ 0.987v, custom curve dropping to +60 @ 1.062v+. VRAM +1250.

Tested with Division 2 @ 1080P DX12 all max settings no FPS cap.
Card power throttles pretty hard. Running EVGA XC3 Ultra BIOS for better fan control and ~10-15w power power limit. Also, fans are NOT powered by the card so that power draw is not on the card. Re-wired the fans to run +12v and GND from a motherboard header and PWM + RPM from the card.

2479376
 

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I placed two large copper heatsinks with thermal pads underneath and a fan in the back pulling air out and it lowered the mem temps from 106C to about 98C. I further decreased the temps to 94C by lowering mem OC from +1500 to 1350 mhz with only 2 mh/s hit. This is an EVGA RTX 3090 FTW3 Ultra with stock bios. Room ambient temps are around 21 degree C (70F).
 

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Those Mining temperatures ?? :) I had 100% same memory temps under mining as You before changing to gelid pads :)
Mining is 88 degrees to 84 degrees friend.
Those are gaming temperatures with 450watt vbios.

I had 100 degrees in mining but then added thermal paste to memory modules on gpu. I have a rtx 3080 card with evga ftw3 ultra pcb. I am currently using the hybrid kit. Temperatures now are very decent and managable. Thus, I am not going to apply gelid pads. However, they do seem atttactive.
 

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I placed two large copper heatsinks with thermal pads underneath and a fan in the back pulling air out and it lowered the mem temps from 106C to about 98C. I further decreased the temps to 94C by lowering mem OC from +1500 to 1350 mhz with only 2 mh/s hit. This is an EVGA RTX 3090 FTW3 Ultra with stock bios. Room ambient temps are around 21 degree C (70F).
I got similar results with placing this heat sink atop my 90 FE with the thermal paste that came with it because I'm a lazy git. I also threw a spare arctic pwm 120mm on top that I had to help push air through it.

+1500 mhz on mem and it sits at around 100c when mining. Usually average around 118-125 mh/s. Bringing the mem down to 1200-1300 does drop the temperature a 4-6 c iirc at the cost of a few mh/s just like you. My ambient was also similar at 23c or 74f.

This is also with the re-pad for reference.
 

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Discussion Starter #12
I've got an AMD wraith on top of the backplate (Gigabyte 3090 OC) and temps still go up to 106 under heavy load, ie mining. Therefore, I've come to the conclusion that IF I want it any cooler (temps below 100C), I'll have to crack it open and replace the thermal pads on the VRAM. However I am a little worried that this might potentially invalidate the warranty. So I'm wondering if

A) leave it alone as it is and allow the temps to stay at 106 degrees and if/when I have a problem RMA at that time.

B) replace the thermal pads and possibly invalidate the warranty.

C) Throttle usage so that temps stay around 102C
 

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I got my Gigabyte Gaming OC 3080 to stay under 80c junction now with some pretty ghetto mods..

Accelero IV backplate with corresponding thermal pads, liquid ultra on the core, stock pads on the cooler, fans + shroud removed, fitted with 2 140mm high airflow fans on the open cooler to blow a bunch of air more directly on to the PCB / cooler part for the memory.

IMG_20210222_121819.jpg

IMG_20210222_121849.jpg

IMG_20210222_121841.jpg

Result with gaming bouncing off the power limit constantly for quite a long period of time to properly heatsoak everything. Completely stock with no pads on the stock backplate it would hit about 68c core, 79c hotspot and 98-102c junction with the same +120 core +1250 memory but effective clocks would be at least 30-40Mhz lower.

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I don't have a GDDR6X card, but I have some info that may be of use! You can calculate the gradient across a thermal interface if you know thickness, K value, heat output, and area of the heat source. The results surprised me when I was shown the equation.

(thickness in meters X watts of heat) / (area of heat source in sqr meters X W/mK)

With memory chips, the die is much smaller than the plastic package, I'm not sure the die size of GDDR6X, but GDDR5 is roughly 5x5mm. Since the package is a poor conductor of heat, the important dimension to consider is die size.

So for a rough example : 1.0mm 6W/mK pad and 5W of heat coming from a 5x5mm die :

(0.001m x 5W) / ((0.005m x 0.005m) x 6W/mK) = 33.3c gradient

Meaning the chip will theoretically always be 33c hotter than the heatsink. Obviously a lot of heat can be dissipated into the board, so this is a very rough example. Calculating it all accurately is above my pay grade.

If you decrease the gap to 0.5mm, you cut the temp difference in half. If you were to use 15x15mm copper shims and quality thermal paste directly on the memory chips themselves, the gradient between the chip and copper should be relatively small, and that would spread the heat to 9x the area, in the example. So ignoring the inefficiency between chip and shim, that's an 18x improvement. Again, this is extremely oversimplified as far as actual thermodynamics, but you can at least see why thermal pads suck for cooling memory.

Would be awesome if someone with a 3080/3090 could try some shims directly on the chips and thinner pads between shim and cooler / backplate :)

There's also TG-PP10, a 10W/mK thermal putty that you can get from Digikey. No need to worry about having the perfect thickness of pads if you use that, and you could fill more of the gap with a thicker shim for better cooling.
 

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I mean if you're rich you can buy this 1.5mm 17.8 w/mk pad.


.....or 1.0mm...


Ok that was fun right?

Back down to earth:
14.5 w/mk 100mm x 100mm x 1.5mm

And 1.0mm ...

Yeah these are expensive but these are better than buying four 60mm * 50mm 17 w/mk Fujipoly thermal pads for $37 each (which would be 120mm * 100mm) for $148 total.

Ok for everyone else:

These are actually not a bad purchase.
12.5 w/mk, 160mm * 160mm, 0.5mm thickness for $37

12.5 w/mk, 160mm * 160mm, 1.0mm, for $60

1.5mm version: $84: TG-A1250-160-160-1.5 t-Global Technology | Fans, Thermal Management | DigiKey

2.0mm version: 112 (ouch): TG-A1250-160-160-2.0 t-Global Technology | Fans, Thermal Management | DigiKey

Unfortunately the 1.5mm and 2.0mm are out of stock in 160mm * 160mm size so you would have to step down to 100mm * 100mm or something. At that point, for 1.5mm thickness, better to buy three Thermalright Odyssey 1.5mm samples off Amazon. The 1.0mm ones are still okay for when you need 1mm pads.
-------

If you guys have money you might want to buy these instead of waiting for the slow boat from China for Thermalright Odyssey or Gelid 120mm * 120mm pads....
 

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Discussion Starter #16
well I'm a little disappointed. I put a spare AMD wraith cooler on top of the backplate with a thermal right thermal pad which did help by a couple of degrees but nothing dramatic. The junction temp is pretty stable at 102-103C @85% fan speed with 105 MH/s. Any attempts to get it higher results in temps hovering at 104-106C. Therefore, I'm pretty much convinced that no amount of cooling on the backplate will result in any meaningful improvement in temps. I'll probably have to replace the thermal pads if 2.0mm pads ever come back in stock.
 

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^^ was there any mounting force and is the backplate flat?
 

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backplate is pretty flat, pressed down firmly supporting the card from below to ensure good contact and released...

the real problem is probably inadequate OEM thermal pads. Replacing the Gigabyte seems to be a bigger hassle than most and the 2mm pads are out of stock everywhere.
 

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I thought that looked like the stock backplate on my Eagle OC. The gap is too wide, plate too thin, and there were no stock pads on the backplate of mine. My Bykski backplate is twice as thick, and I've added thermal pads behind core, memory, and VRMs. Even put a finned copper server heatsink on it. Both that and the plate gets hot to the touch, so it's working. Stock plate did not get hot, just luke warm.
 
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