SLI or Nvlink configuration

[michel_baudbovy]

Hello,

Question for a SLI/Nvlink configuration specialist.

I' have been using Sketchup Pro 2018 and V-Ray 5 for monthes and it when all fine (CUDA rendering incl), but, I needed to upgrade my previous setup to speed up my rendering.

The idea was to add a second graphics card and bridge them with a SLI bridge..

My new setup is:

• Windows: 10 64 bits
• 4 x 8 Go Corsair DDR4 Ram
• Intel i7.7700 CPU @ 3.60GHz
• 2 x NVIDIA GTX 1080ti
• 1 x Gigabyte SLI bridge (flexible cable 10 cm).
• NVIDIA Pilot: 497.09

Unfortunately this new setup does not use the GPU for rendering as it did when i used only one graphic card.

Now, in CUDA mode, my processor still works at its max capacity (99%) but my 2 GPUs speed droped down to 1%.
It's a lot slower as before (when I used only one graphic card).

I have no error message in my V-Ray log. If I use a graphics computing test program like "Fur Mark" I can see my 2 GPUs working together. Why doesn't it also work with VRay?

What is wrong with my configuration?

Should I switch to Vlink? I've read posts on the forum that say "yes" and others that say "no".
Is that the problem?

Thanks for your help.

[Muhammed_Hamed]

Hey @michel_baudovy and welcome to the forums

You don't need SLI to use 2 GPUs in V-Ray, it is better to disable that in Nvidia's control panel, and you can even remove the physical bridge. On pascal GPUs, SLI is only usable for a handful of games but it can introduce issues to DCCs and Adobe applications
After that download V-Ray's Benchmark, and run the Cuda test on each GPU alone then on both GPUs. This will help us in troubleshooting, post your scores here

Best,
Muhammed

[michel_baudbovy]

Hi,

Thank you for your first answer. Here are the results:

• 1st GTX only: https://benchmark.chaosgroup.com/v5/vray-gpu-cuda/20391
• 2nd GTX only: https://benchmark.chaosgroup.com/v5/vray-gpu-cuda/20392
• both GTX: https://benchmark.chaosgroup.com/v5/vray-gpu-cuda/20393

All scores without CPU

Best rgards,

Michel

[Muhammed_Hamed]

Thanks Michel

The first GPU has a very bad score somehow, did you disable SLI from Nvidia control panel?
during the benchmark on 2 GPUs, could you check task manager for temperature? can you upload me a picture of the GPUs in the system?
This seems to be a hardware-related issue. We can try and troubleshoot that for you as well

Best,
Muhammed

[michel_baudbovy]

Hi,

Yes, SLI has been deconnected in the NVIDIA's control panel. I also reistalled NVIDIA's pilot: (497.09)

My new scores are :

• 1st GTX only: https://benchmark.chaos.com/v5/vray-gpu-cuda/20409
• 2nd GTX only: https://benchmark.chaos.com/v5/vray-gpu-cuda/20410
• both GTX: https://benchmark.chaos.com/v5/vray-gpu-cuda/20411
• GPUs + CPU: https://benchmark.chaos.com/v5/vray-gpu-cuda/20412

During the tests, temperature of the CPU climbs up to 65 Celsius degrees.

Here below a picture... Is it what you were looking for?




Best regards,

Michel

[Muhammed_Hamed]

We can setup remote access and take a look at your machine
It is odd how 2 GPUs perform as 1 in your case. I will coordinate with my colleagues and get back to you

Best,
Muhammed

[michel_baudbovy]

Yes we can. When will it be convenient for you ?
Bst,
Michel

[Muhammed_Hamed]

We will get in touch soon

[michel_baudbovy]

OK.. i'm waiting.

[slavcho.brusev]

Hello michel_baudbovy

I have opened a ticket(#24887) in our support system and have sent you an email so we can arrange a remote meeting.

If you haven't received the email, please log in a request here and paste the ticket number in this thread so I can track it.

Thank you!

[michel_baudbovy]

@slavcho.brusev Thank you.
With the re-installation of the last NVIDIA supported driver (497.09) and your support, it's now all cleared.
Best regards,
Michel

[slavcho.brusev]

You are welcome