Two GPUs are shown - but only one is being used for rendering

Rafa20

After updating windows 10, only one of my 1080ti GPUs is being used for rendering though both GPUs are shown and selected in the render settings!

Here the background. One of my Gigabyte 1080ti founder's edition GPUs conked out. Both were still shown but it rendered just with one. Then I replaced both of them with two Asus 1080ti Strix GPUs and it rendered with both again. 

Then I had some issues with windows and used in the windows powershell admin the function "sfc /scannow", to repair my windows 10 and after it repaired my system, I updated it.

After that, Daz Studio is rendering only with 1 GPU again though both are new and worked right before.

What I did and checked then:

- Reinstalled the nvidia driver a few times and restarted the PC

- Updated BIOS

- Both GPUs are shown in device manager

- In the nvidia control panel, SLI is connected

- I disabled SLI and checked both GPUs if I get a picture, and yes I get one. So both GPUs are working and also the mainboard 16x slots are alright

- Reinstalled Daz Studio

But it's still the same! Bizarrely that if I disable SLI, Daz Studio is rendering with both GPUs. Enabling it back to SLI, and it uses again only 1 GPU.

What could be the problem?

dawnblade

SLI is great for gaming but not for rendering in Iray. Render with SLI disabled and Daz Studio will use both GPUs, assuming the scene doesn't exceed the VRAM of a single video card.

Rafa20

But it's strange because over 1 year I rendered with two 1080ti founders's edition GPUs in "SLI mode" and it used both cards! After replacing them with two new 1080ti Strix it worked also in SLI. But after the windows update it uses only both GPUs with disabled SLI.

fastbike1

Nvidia definitely recommends disabling SLI for working with Iray.

Wallace3D

I am running into the same problem with iray not using both to render ' however it does use both to Process the render' CUDA (device 0) and CUDA (device 1)

when it starts to render both cards are using the GPU Clock then I get GPU 1 18% usage GPU 2 0% usage and CPU 34% after about a min with hundreds of literations a second

it maintains that speed for the remainder of the render until it reaches 100% rendered which takes 5 - 10 min to complete. 

my bigest question is why is it not useing 100% of my GPU's

Rendering in NVIDIA Iray

Compiling Shaders - 0/1

Rendering image

Rendering...

Iray VERBOSE - module:category(IRAY:RENDER): 1.11 IRAY rend progr: CUDA device 0 (GeForce GTX 1080): Processing scene...

Iray VERBOSE - module:category(IRAY:RENDER): 1.5 IRAY rend progr: CUDA device 1 (GeForce GTX 1080): Processing scene...

Iray VERBOSE - module:category(IRAY:RENDER): 1.10 IRAY rend stat : Geometry memory consumption: 10.743 MiB (device 1), 0 B (host)

Iray VERBOSE - module:category(IRAY:RENDER): 1.6 IRAY rend stat : Geometry memory consumption: 10.743 MiB (device 0), 0 B (host)

Iray VERBOSE - module:category(IRAY:RENDER): 1.10 IRAY rend stat : Texture memory consumption: 485.246 MiB (device 1)

Iray VERBOSE - module:category(IRAY:RENDER): 1.6 IRAY rend stat : Texture memory consumption: 485.246 MiB (device 0)

Iray VERBOSE - module:category(IRAY:RENDER): 1.10 IRAY rend stat : Lights memory consumption: 1.80841 MiB (device 1)

Iray VERBOSE - module:category(IRAY:RENDER): 1.6 IRAY rend stat : Lights memory consumption: 1.80841 MiB (device 0)

Iray VERBOSE - module:category(IRAY:RENDER): 1.10 IRAY rend stat : Material measurement memory consumption: 0 B (GPU)

Iray VERBOSE - module:category(IRAY:RENDER): 1.10 IRAY rend stat : Materials memory consumption: 476.203 KiB (GPU)

Visuimag

I have had this issue and I believe it is driver related. Every update after 391.35 shows only one of my Titan Xp's rendering (using GPU-Z), even though both are selected in Studio. On 391.35, I have no such problem.