RTX 3090 SLI/NVLink (Help Please)

[Jarrastafari]

I've watched the GamersNexus video and found a thread elsewhere but can't seem to find any guidance on how SLI/multi-GPU works (or doesn't) for the 3090's.

Since we have our hands on two different brands - a Palit & Zotac (all we could get given the circumstances) - what can we expect in regards to getting this to work? I assume an open bench system, lots of alignment issues and the need for an NVlink/bridge adaptor but can't seem to see what exactly it is we'd need there.

I don't specifically care about game performance (this would be a nice "bonus") as I'm more a game developer than a gamer these days. This is also just a stop-gap until A6000's are available.

Advice most appreciated,
Thanks.

 

[Nablaoperator]

Great we have a live experiment going here!

Other than what you've suggested you will need a SLI capable motherboard.

The nvlink is 4 slots wide so you'd like to choose a mobo to match the spacing.

If those cards are not aligned then other than what you have suggested, may also try flexible vertical pcie mounts with case mods.. haven't looked at this in detail.. but you will need 1 of them to be much longer.. depending on your case width this setup can run with closed chasis

Drivers will take care of the rest..

I am keen to know if DX 11 profiles can still be forced.. maybe if you have some time, you can probably run witcher 3 using default sli settings on the control panel (afr1/afr2) and let us know how it scales...

If you have more time at your hands, then probably try forcing profiles using Nvidia inspector to see if it scales in dx11 apps..

 

[Jarrastafari]

Thanks for the in-depth reply. I'll see how far I get and report back.

Appreciated.

 

[PrincessFrosty]

NVlink/SLI is supported for the 3090s only, I have seen reviewers mixing and matching video cards to do this so that does seem to work. Spacing is a serious problem everyone has had so far, these cards are between 2 and 3 slots and you need 2 of them in the rig, and the SLI bridge that Nvidia make is fixed length and motherboard spacing is also a factor, again most of the reviewers testing this so far have had spacing problems and used open air benches with PCIe riser cables to get it working.

They've also stated that driver support for SLI is now ending and that SLI support will have to be baked into the specific game/application, I think there's like 10 games or so that can use it right now and quite frankly I don't see anyone else wasting their time on it from now on, it's just way too niche at this point, for gaming it's effectively dead.

 

[Jarrastafari]

Thanks, PrincessFrosty. My interest in this is in development work so I had read about the support being left to developers (dropped).

Funnily enough, my friend just sent this which is timely...

 

[PrincessFrosty]

Thanks, PrincessFrosty. My interest in this is in development work so I had read about the support being left to developers (dropped).

Funnily enough, my friend just sent this which is timely...

There's an overclocking spat going on between a few of the hardware youtubers that cover a lot of the pain of getting this working that I'd highly recommend watching before you try doing it.

Gamers Nexus here https://www.youtube.com/watch?v=-OaJRBDdPfg
JayzTwoCents here https://www.youtube.com/watch?v=QbQoLUbgrPc
Paul's Hardware here https://www.youtube.com/watch?v=InPsPsguD2Y

Quite funny because they have a nice back and forth colab thing going on where they're torturing each other off the benchmarking leaderboard starting on air and stock settings, moving up to water cooling and cooling with ice and eventually on to LN.

 

[Jarrastafari]

To get this going I figure I'll need to purchase an NVlink connector, new mobo and PSU.

1. An Asus NVlink should do or do I need a one specifically for 30 series? The one I saw on the nvidia website is gone.

2. I think the only 4-slot spaced board is the Godlike, correct?

4. As always the mystical non-science of PSU rumor dictates I'll need a 2000w PSU but I see these 'tubers pulling it off around 1200-1300w right?

Also, this will be in a neely bought LianLi Dynamic with my air-cooled 2700X until sometime after 5th November when I can (hopefully) get my hands on a 5900 or 5950X and a suitable AIO. What else could go wrong! Hah.

 

[Nablaoperator]

You will need the 30 series nvlink.. atleast that's what Nvidia says

Godlike supports SLi but am not sure abt the spacing

​

PSU atleast 1200W.. but you can think of future proofing cuz psu prices wont be coming down

 

[Jarrastafari]

Had ordered an X570 Godlike and HX1200 plus NVlink for Monday delivery but cancelled as I remembered I needed to check the fingers matched up first.

Cards arrived today so I measured the positioning of the fingers on the two cards and they're both around 1.7-1.8mm from the rear mount so I think we should be good to go now.

However, it seems I now can't find a 30' series NVlink anywhere at this time. Bummer!

 

[QueueCumber]

If you manage to get RDR2 running with your 3090 SLI, do post what you did to force two gpus to work. Spent hours trying to get it up and running today...

 

[Raiden85]

If you manage to get RDR2 running with your 3090 SLI, do post what you did to force two gpus to work. Spent hours trying to get it up and running today...

MGPU support should work instantly in vulkan mode without doing anything as it did when I had 2x 2080 Ti's. MGPU/SLI is not supported in DX12 for that game though.

 

[QueueCumber]

MGPU support should work instantly in vulkan mode without doing anything as it did when I had 2x 2080 Ti's. MGPU/SLI is not supported in DX12 for that game though.

I agree completely. It should. But it didn't for me. I found a work around though, and now it's up and running.

 

[QueueCumber]

Here is what worked for me in case anyone else finds they are trying to run 3090s in SLI with Red Dead Redemption 2 (RDR2) in Vulkan and are having the below issues:

***Make sure SLI is enabled in the Nvidia Control Panel***


1) First issue was getting RDR2 to run at all with SLI Enabled in the NVidia Control Panel. Without this change, my SLI would just result in black screens with sound for both the benchmark and the game itself.

[a] Solution: changing transferQueuesEnabled from 'false' to 'true' in the system.xml file located in C:\Users\*****YOUR USER NAME ON YOUR PC*****\OneDrive\Documents\Rockstar Games\Red Dead Redemption 2\Settings\system.xml

Make sure to edit in notepad and not to allow any formatting changes to be made or added. Also, the file won't show the lines that you need to edit unless you open it in something like notepad or txt edit (xml viewer hides the lines for some reason...).


2) The next issue was getting the SLI to actually enable for the 3090s. This I suspect has to do with some kind of conflict between programs accessing and changing the nvdrsdb0.bin and nvdrsdb1.bin files independently of each other for some reason.

[a] Download and install nvidiaProfileInspector. Change the following settings on Red Dead Redemption 2 profile:

• In section 5 - Common: change Power Management Mode to Prefer Maximum Performance
• [optional] Antialiasing - SLI AA to Enabled
• Change the 'Number of GPUs to use on SLI Rendering Mode' to '0x00000002 SLI_GPU_COUNT_TWO'
• Change the 'NVIDIA predefined number of GPUs to use on SLI rendering mode' to '0x00000002 SLI_PREDEFINED_GPU_COUNT_TWO'
• Change the 'NVIDIA predefined SLI mode' to ''0x00000003 SLI_PREDEFINED_MODE_FORCE_AFR2'
• Change the 'SLI rendering mode' to '0x00000003 SLI_RENDERING_MODE_FORCE_AFR2'

[c] After applying the above changes immediately change the nvdrsdb0.bin and nvdrsdb1.bin files (Location: C:\ProgramData\NVIDIA Corporation\Drs) to 'read only'

• Note: You will have to go to Appearance and Personalization in the Folder Options in Control Panel and select 'Show Hidden Files, Folders, and Drives' to access these easily.

 

[Nablaoperator]

Here is what worked for me in case anyone else finds they are trying to run 3090s in SLI with RDR2:

***Make sure SLI is enabled in the Nvidia Control Panel***


1) First issue was getting RDR2 to run at all with SLI Enabled in the NVidia Control Panel. Without this change, my SLI would just result in black screens with sound for both the benchmark and the game itself.

[a] Solution: changing transferQueuesEnabled from 'false' to 'true' in the system.xml file located in C:\Users\*****YOUR USER NAME ON YOUR PC*****\OneDrive\Documents\Rockstar Games\Red Dead Redemption 2\Settings\system.xml

Make sure to edit in notepad and not to allow any formatting changes to be made or added. Also, the file won't show the lines that you need to edit unless you open it in something like notepad or txt edit (xml viewer hides the lines for some reason...).


2) The next issue was getting the SLI to actually enable for the 3090s. This I suspect has to do with some kind of conflict between programs accessing and changing the nvdrsdb0.bin and nvdrsdb1.bin files independently of each other for some reason.

[a] Download and install nvidiaProfileInspector. Change the following settings on Red Dead Redemption 2 profile:

• In section 5 - Common: change Power Management Mode to Prefer Maximum Performance
• [optional] Antialiasing - SLI AA to Enabled
• Change the 'Number of GPUs to use on SLI Rendering Mode' to '0x00000002 SLI_GPU_COUNT_TWO'
• Change the 'NVIDIA predefined number of GPUs to use on SLI rendering mode' to '0x00000002 SLI_PREDEFINED_GPU_COUNT_TWO'
• Change the 'NVIDIA predefined SLI mode' to ''0x00000003 SLI_PREDEFINED_MODE_FORCE_AFR2'
• Change the 'SLI rendering mode' to '0x00000003 SLI_RENDERING_MODE_FORCE_AFR2'

[c] After applying the above changes immediately change the nvdrsdb0.bin and nvdrsdb1.bin files (Location: C:\ProgramData\NVIDIA Corporation\Drs) to 'read only'

• Note: You will have to go to Appearance and Personalization in the Folder Options in Control Panel and select 'Show Hidden Files, Folders, and Drives' to access these easily.

I am interested in knowing if theres a way to force DX11 SLI on 3090s..would you be able to test that as well?

 

[QueueCumber]

I am interested in knowing if theres a way to force DX11 SLI on 3090s..would you be able to test that as well?

I would love to but would need help figuring out how to do so. I've never forced SLI before, but if it is possible that would be great, because Destiny 2 is one of the games I love playing and SLI would bring the max 4k settings to my monitors highest refresh rate (144Hz/144fps).

If you have links or any resources that are helpful, I'll get to it today.

I'm guessing I can use the nvidiaProfileInspector to alter it game by game?

 

[Nablaoperator]

I would love to but would need help figuring out how to do so. I've never forced SLI before, but if it is possible that would be great, because Destiny 2 is one of the games I love playing and SLI would bring the max 4k settings to my monitors highest refresh rate (144Hz/144fps).

If you have links or any resources that are helpful, I'll get to it today.

I'm guessing I can use the nvidiaProfileInspector to alter it game by game?

I have generally found that the SLI Mode:Enable Alternate Frame Rendering 2,
... generally works on all games even on very old games from early 2000s with my 2080ti setup.
Failing which, I look this thread up at 3dcenter
https://www.forum-3dcenter.org/vbulletin/showthread.php?t=509912

 

[QueueCumber]

I have generally found that the SLI Mode:Enable Alternate Frame Rendering 2,
... generally works on all games even on very old games from early 2000s with my 2080ti setup.
Failing which, I look this thread up at 3dcenter
https://www.forum-3dcenter.org/vbulletin/showthread.php?t=509912

Very cool thread! Thank you. That will be very helpful moving forward.

I hope it does work like that still, because it might make it worth my while to use these in SLI more often.

 

[QueueCumber]

I have generally found that the SLI Mode:Enable Alternate Frame Rendering 2,
... generally works on all games even on very old games from early 2000s with my 2080ti setup.
Failing which, I look this thread up at 3dcenter
https://www.forum-3dcenter.org/vbulletin/showthread.php?t=509912

It doesn't appear to be working with Destiny 2 so far with it set to count two gpus and AFR2. When you say "SLI Mode: Enable", which specific settings do you mean? I don't have that setting in the nvidiaProfile inspector. Is it in another file somewhere?

 

[QueueCumber]

No luck in AFR or SFR either...

This is with me messing with the settings I listed above. I didn't see D2 on the website link you sent (likely because it already has SLI that works automatically with older cards while I am trying to make two 3090s with no driver support work with it--maybe I need to change settings in Inspector that would be left alone if I had older SLI cards, like turning SLI explicitly off and then forcing it like it is a game without SLR?).

 

[Nablaoperator]

When you say "SLI Mode: Enable", which specific settings do you mean?

That's available inside NV control panel.. where you will also find other settings like ambient occlusion, antialiasing, anisotropic filtering etc.

So you should be able to choose from 3 SLI modes:

Nvidia optimal (it picks up the game profile)
AFR1
AFR2

I don't know if this is available for ampere cards though.