Active backplaet 4090

[allen5055]

Anyone think it's worth paying $150 more for an EKWB 4090 gpu block with an active backplate. No memory on the rear PCB so seems extraneous but kinda cool.

 

[hititnquitit]

Anyone think it's worth paying $150 more for an EKWB 4090 gpu block with an active backplate. No memory on the rear PCB so seems extraneous but kinda cool.

Does it have rgb? 😉

 

[allen5055]

Seems a waste, I decided against it. Doubt it'll make much difference. My card is the zotac amp extreme 4090 which is the weakest of the brands anyways, they say it's more power limited by software.

 

[kirbyrj]

I don't think you need it. My 4080 runs a lot cooler than my 3090 ever did under high load situations.

 

[Zarathustra[H]]

At first I thought it was a wasteful money grab.

Then I started looking at naked 4090 pics (safesearch enabled ) It does look like there are some VRM's and caps on the back of the board, at least on some designs, so it might not be completely useless. That, and chips aren't unidirectional, they will give off heat on the bottom too, so in modern ridiculously high power draws, it might make sense to remove heat wherever you can remove it.

Either way it is moot for me, as the damn thing won't fit.

As I posted in this thread, if you want one, make sure you have 15mm of clearance from the center of the PCIe slot on the back of the board, otherwise it won't fit.

If my board winds up feeling too hot to the touch on the back, I may just wind up grabbing a large black oxide heatsink from ebay or amazon and slapping it on the back of the board using some thermal tape. It might help at least a little bit, and shouldn't look TOO terrible.

 

[vegeta535]

Not worth the extra cost on a 4090 since all the memory chips are on the front unlike the 3090.

 

[Zarathustra[H]]

Not worth the extra cost on a 4090 since all the memory chips are on the front unlike the 3090.

I think it depends on the board.

This is a Gigabyte 4090 Gaming OC design: (source: Techpowerup)

There are certainly some components on the back of the board. Not sure what they are. Part of the VRM's? (I googled the markings, and didn't come up with anything)

They might generate some heat. Who knows. Looks like there were thermal pads covering them based on the residue, and I'm guessing that was there for a reason.

Once I get mine (an MSI Gaming X Trio) I'll measure the back and see how hot it gets.

Might be a little while though. Waterblock won't arrive until 01/20, and before I get it installed I am going to flush and do some drilling to get my pump aligned, etc.

I'll do a measurement with the stock cooler before then, but that won't be representative, as the temps on the back of the board generally drop significantly once you better cool the chip from the front.

 

[MooCow]

I installed the EK 4090 front and active backplate for my friend's Reference Nvidia 4090. He says it runs cooler than the 3090Fe at around 560 - 580 watts. I don't have exact numbers, but we're pretty sure the backplate helps.
And yeah it didn't originally fit on his motherboard, we had to remove the OLED screen below the CPU socket.

 

[NattyKathy]

The stuff on the back of GPU PCBs (other than 3090 ofc) are capacitors, various controllers and minor components for the VRM, and sometimes shunt resistors. Nothing that generates a ton of heat (or even needs cooling), but the PCB itself has so much copper and vias that it is possible to dissipate some heat from the GDDR and Core thru the PCB and out the back. Not like a stupendous amount but backplate cooling isn't totally useless if you're looking for the absolute best thermal performance regardless of cost.

 

[Zarathustra[H]]

Alright, so my 4090 arrived, and I popped it in the testbech machine to make sure it works while I wait for my waterblock to arrive on the slow boat from Slowvenia.

My testbench resides in a Phantecs Enthoo Pro.

I wound up with the MSI Gaming X model. Not because I specifically wanted this model, but because it was what I could find in stock without too much retail scalping.

I had to pull my 10gig NIC and remove the hard drive bays in order to make it fit.

Even though this is probably the weakest cooler of all the 4090's out there, as it lacks a vapor chamber, it still does pretty well. At stock fan settings I never saw the fans exceed 31%, and it was pretty damn silent at those speeds.

I grabbed my FLIR camera to see what the heat on the back looked like:

These are taken from the CPU cooler side. The red blob in the background is the PSU.

The ~52C hotspot is the backplate.

This was at a room temp of 69F (nice) with a GPU load temp of ~65C.

So, the backplate does get pretty hot at stock fan speeds with the stock cooler.

In order to see if it was the components on the back causing this heat, or if it was just excess heat from the CPU, I manually overrode the fans to 100% to remove as much of the GPU heat as possible, and leave the back plate with only the heat from the components on the back, in an attempt to estimate what it would look like with a water block installed.

These are the results:

Note that the color scale adjusts when the temperatures change. Here we can see that with the fans at 100% the hottest spot in the image has shifted to the PSU, which is 37C.

The back of the GPU by comparison is much cooler. Probably about 28C but my aim was off, as I was at an awkward angle with the CPU cooler in the way. This suggests that most of the heat that loaded up the backplate in the past two pics came from the GPU.

Based on this, I am going to make an educated guess that for the 4090 an active backplate is probably not necessary. A normal water block will remove the heat from the front, and the backplate should thus not get too hot.

That said, this was on my old testbench with an i7-3930k, and the CPU is likely holding the GPU back, so it is likely running a little cooler than it otherwise would.

Once my water block gets here and I have it installed on a capable CPU without a CPU tower cooler blocking the view, I will update with new FLIR images and temperature estimates.