My 3080ti with the optimus block does 60c max on the mem so something is up with your mount :)

I have a Rtx 3090 FTW3 ultra with the OP block my memory junction temp run under full load around 74c. Used KP paste and all stock pads that came with . Kingpin HC block under load runs 20 to 22 c hotter. I think re do of block mounting should help.

telehog
I have a Rtx 3090 FTW3 ultra with the OP block my memory junction temp run under full load around 74c. Used KP paste and all stock pads that came with . Kingpin HC block under load runs 20 to 22 c hotter. I think re do of block mounting should help.

Did you use the thermal pads that came with the block or something else?

MIab84

telehog
I have a Rtx 3090 FTW3 ultra with the OP block my memory junction temp run under full load around 74c. Used KP paste and all stock pads that came with . Kingpin HC block under load runs 20 to 22 c hotter. I think re do of block mounting should help.

Did you use the thermal pads that came with the block or something else?

I used all stock pads !

MIab84
Hey guys,

So I installed an Optimus waterblock and XL backplate, used the full sheet of Fujipoly for the back plate but for the front I used Odyssey pads, correct size (.5mm). Thermal grizzly for paste on core.

During full load, my core gets to about 40c but my memory is at 90c!

My system is 3 360mm rads, and I have a 5950X at stock speeds on the loop as well.

What gives? I thought It would be way better temps

When you say "full load" are you talking about gaming? Benchmarks? ...Or mining? Because if you're talking about mining and you're running a big mem overclock then you're doing just fine. Anything else, well, yeah, redo your mount. 

The temps sound very wrong.  I have the Optimus block on my 3090 FTW3 Ultra and the GPU VRAM during multiple runs on Port Royal/Time Spy is no where near your temps even with an oc.  
 
Why did you need to change the pads and did you use the same thermal pads on the rear that come with the block?  Or did you get them from another source?  
 
 
 
 

the_Scarlet_one
Are you reading the memory temps, or are you reading ICX mem temps?

If you are looking at Precision Mem temps in the ICX menu, try using GPU-Z and reference the memory temps in there.

I'm reading mem temps from HWinfo.

Will EVGA RMA this card??

For reference, I also have a 3090 FTW3 with the Optimus block, so I just ran the Furmark stress test now for ~20min and with no OC. How long did you let your furmark stress test run for?
During my run, the VRAM junction temp hit a max temp of 76C and below is a hwinfo snippet with some more details.
Also, my case temp went from 27C-29C and the fans were going at ~60% speed for this run.
 

 
Since the hot VRAM on the back of the card is passively cooled with the Optimus backplate, I wouldn't expect your radiators and loop to completely determine the VRAM temps.
Instead, I would expect your case temp and airflow on the rear side of the card to also impact the VRAM temp.
 
And, I would not recommend tightening the screws by too much.
The way you described the retightening sounds about right, and you shouldn't need to exert yourself doing so because the PCB can bend if you overtighten.

If it really bugs you, you could get an EKWB block, which has an active backplate and would cool the VRAM better but at a cost of increased GPU temps.
 
If you want the best of both worlds, Optimus may also create an active backplate for their FTW3 blocks, however, they are still stuck working on Kingpin blocks people ordered 6+ months ago, so who knows when their FTW3 active block would be ready (if they decide to create one).