This was written before Ek Nickel backplates became available. I highly recommend getting one for better temperatures. This mod is inherently risky.
 
Hi Folks,
I have gone on a journey trying to get my Barrow block to work. As some of you may know, the barrow block re-uses the existing backplate. Getting the right size of backplate thermal pads to work while not disrupting the PCB and front side thermal pads seemed to be almost impossible. To get everything working I decided to remove the thick thermal pad and backplate constraint. Doing this resulted in an average TJ max Temp of 73.2°C after 17 hours of torture testing.
WHY WOULD I EVER DO THIS?!?!?
 If you use your 3090 on long duty cycles that are VRAM intensive the back chips will get over 100°C. This is unacceptably high and good backplates are not currently available for FTW3's. Mining is currently paying $400 a month and if we are going to do it, lets do it RIGHT.

 
MATERIALS NEEDED:
2x Alphacool 14x14mm Copper heatsinks-link (you need to fit 12 heatsinks on the chips and the packs only come in 10. cheaper aluminum ones or smaller copper ones are untested.)
A full tube of thermal paste (Non-electrically conductive whatever you have/ get your hands on)
A 140mm Fan- I will eventually use a Noctua 3000rpm industrial 
 
Method
1. Remove backplate
2. Apply paste to heatsink (about a screw head size each)
3. Apply heatsinks one at a time and make sure to spin them around until thermal paste is evenly distributed. (you will have overhang on the banks of 4, take care to avoid the power regulator chips toward the bottom of the PCB)

4. Position 140mm Fan directly over the heatsinks with the fan hub preferably directly above the back of die. (you will need to get a little creative on mounting the fan. 2x of these will allow the fan to clear the heat sinks)
 

Good thermal tape will be effective too.
 
Why are there exposed thermal pads?  They'll probably dry out left like that.

Should add your stuff to this thread, I'm trying to compile stuff for all 3 SKUs/other 3090s as well so people know the layouts if they want to keep their backplate, or not:
 
https://forums.evga.com/3090-Kingpin-Get-that-backside-VRAM-cool-Also-Thermal-Pad-size-backplate-side-m3219773.aspx 3090 FTW3 I already did a bit of a layout for "if you want to thermal pad/heatsink all the things"

_Gir_
Good thermal tape will be effective too.
 
Why are there exposed thermal pads?  They'll probably dry out left like that.

I was worried the thermal tape would leave too much heat transfer on the table.

Those thermal pads are a holdover from prior mount attempts. They are basically trash now.

Razgriz2006

Dabadger84
Should add your stuff to this thread, I'm trying to compile stuff for all 3 SKUs/other 3090s as well so people know the layouts if they want to keep their backplate, or not:
 
https://forums.evga.com/3090-Kingpin-Get-that-backside-VRAM-cool-Also-Thermal-Pad-size-backplate-side-m3219773.aspx 3090 FTW3 I already did a bit of a layout for "if you want to thermal pad/heatsink all the things"

Sure do i need to add it or do you want to add it to the first post?

I wanted to post my hwinfo temps but ran over the 500mb limit.

You can post it yourself, I'm trying to get us a database going so to speak of informations about how/where to do heatsinks whether people want to put the backplate back on or leave it off.
 
I found a page dealing with the FE model, plan to do some diagramos on that next.
 
It's actually really hard to find 3090 XC3 PCB shots O_o and I don't get why.  They definitely exist. lol

"Easycargo 10pcs 14mm VRAM Copper Heatsink + pre Applied 3M 8810 Thermal Conductive Adhesive Tape for Cooling Cooler GPU Chips VRAM VGA RAM GPU (14mmx14mmx4mm) (Copper 14mm)"
I bought a set of those 2 years ago for my 2080ti that I never ended up using. I'll report back my finding with them coupled with a fan. 
 
*edit* I tried them with a 120mm fan and 80mm fan. They didn't perform any better than the stock backplate and lacked adhesion. 

Razgriz2006
 if we are going to do it, lets do it RIGHT.
 

 
Please cover those bare pads with heatsinks... That's not right at all. 

During mining I was noticing a ton of throttling on my b-stock 3090 ftw3 ultra. I looked into it deeper and noticed there was no contact on the top thermal pads to the memory. It seems the PCB has a curve to it as well from the main heatsink mounting pressure. Is this normal? After replacing the pads, I ended up using zipties and another heatsink to apply a little pressure, which solved the problem.
 

 

 
After the fix:

 

92 is fine 24/7. Even 110 throttling should be safe. I haven't heard of any damage from it.

Hey Folks,
 
I am the OP of this and this was written before Ek Nickel backplates became available. I highly recommend getting one for better temperatures. This mod is inherently risky.

Gtrack- The factory backplates are inherently susceptible to bending. its not your PCB that is bending... its your backplate