Second GPU not being used for rendering.
jas_va_26
Posts: 74
in The Commons
So when I open task manager the second GPU in my system is sitting there idle while the first one is maxed out at 100%. I have two 1080TI's, No SLI, Both are selected in the advanced options. Anyone else run into this?
Daz 3D is part of 
Connect
DAZ Productions, Inc.
7533 S Center View Ct #4664
West Jordan, UT 84084
Licensing Agreement | Terms of Service | Privacy Policy | EULA
© 2025 Daz Productions Inc. All Rights Reserved.
Comments
Oh I should also note only the first card is being used for monitors.
Occasionally, I'll hit a situation where only one of my GPUs is rendering. This is usually when my scene size is approaching the available GPU memory, and Daz bypasses one of the GPUs, presumably because that GPU's memory also contains other things (other programs, etc.). Or on the first pass, both GPUs render, but on the second pass, one is left idle (I have no theories on this one).
In some experimentation if I unselct the first card and only have it set to the second card, it doesn't use the GPU at all on either card, only the GPU memory and CPU.
I have almost the same situation, but I kept the SLI installed. I gave up trying to get it to work though, as I experimented with a bunch of different options and found no difference no matter what I tried.
I decided to leave the SLI in place after all the testing just because it does function for other programs.
Some other notes, it is using memory on the second card, however the '3d' performance graph on that card sits at 0%, while the one on the first card is pegged at 100%. Looking at the log file is claims to be using the card for the render:
2018-04-19 15:17:07.856 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Updating geometry.
2018-04-19 15:17:07.890 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Using OptiX Prime ray tracing (3.9.1).
2018-04-19 15:17:07.890 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Importing scene graph.
2018-04-19 15:17:07.890 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Importing geometry.
2018-04-19 15:17:09.507 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Geometry import (1 object with 7508k triangles, 1 instance yielding 7508k triangles) took 1.617151
2018-04-19 15:17:09.509 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Updating materials.
2018-04-19 15:17:09.594 Iray INFO - module:category(MATCNV:RENDER): 1.0 MATCNV rend info : found 756 textures, 0 lambdas (0 unique)
2018-04-19 15:17:09.615 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Emitter geometry import (13 light sources with 13254 triangles, 1 instance) took 0.00s
2018-04-19 15:17:09.615 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Updating environment.
2018-04-19 15:17:09.625 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Updating lens.
2018-04-19 15:17:09.625 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Updating lights.
2018-04-19 15:17:09.625 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Updating object flags.
2018-04-19 15:17:09.625 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Updating caustic portals.
2018-04-19 15:17:09.625 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Updating decals.
2018-04-19 15:17:09.629 WARNING: dzneuraymgr.cpp(307): Iray WARNING - module:category(IRAY:RENDER): 1.0 IRAY rend warn : Architectural sampler is deprecated and will be removed in the next version.
2018-04-19 15:17:09.629 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Allocating 1 layer frame buffer
2018-04-19 15:17:09.761 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Using batch scheduling, architectural sampler enabled, caustic sampler disabled
2018-04-19 15:17:09.761 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Initializing local rendering.
2018-04-19 15:17:09.786 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Rendering with 2 device(s):
2018-04-19 15:17:09.786 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : CUDA device 0 (GeForce GTX 1080 Ti)
2018-04-19 15:17:09.786 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : CUDA device 1 (GeForce GTX 1080 Ti)
2018-04-19 15:17:09.786 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Rendering...
2018-04-19 15:17:09.786 Iray VERBOSE - module:category(IRAY:RENDER): 1.18 IRAY rend progr: CUDA device 0 (GeForce GTX 1080 Ti): Processing scene...
2018-04-19 15:17:09.790 Iray VERBOSE - module:category(IRAY:RENDER): 1.4 IRAY rend progr: CUDA device 1 (GeForce GTX 1080 Ti): Processing scene...
2018-04-19 15:17:09.866 Iray VERBOSE - module:category(IRAY:RENDER): 1.11 IRAY rend stat : Geometry memory consumption: 213.731 MiB (device 0), 0 B (host)
2018-04-19 15:17:09.871 Iray VERBOSE - module:category(IRAY:RENDER): 1.12 IRAY rend stat : Geometry memory consumption: 213.731 MiB (device 1), 0 B (host)
2018-04-19 15:17:35.411 Iray INFO - module:category(IRAY:RENDER): 1.11 IRAY rend info : Initializing light hierarchy.
2018-04-19 15:17:35.414 Iray VERBOSE - module:category(IRAY:RENDER): 1.11 IRAY rend stat : Texture memory consumption: 3.55561 GiB (device 0)
2018-04-19 15:17:35.421 Iray VERBOSE - module:category(IRAY:RENDER): 1.12 IRAY rend stat : Texture memory consumption: 3.55561 GiB (device 1)
2018-04-19 15:17:35.500 Iray INFO - module:category(IRAY:RENDER): 1.11 IRAY rend info : Light hierarchy initialization took 0.09s
2018-04-19 15:17:35.502 Iray VERBOSE - module:category(IRAY:RENDER): 1.12 IRAY rend stat : Lights memory consumption: 2.23052 MiB (device 1)
2018-04-19 15:17:35.506 Iray VERBOSE - module:category(IRAY:RENDER): 1.11 IRAY rend stat : Lights memory consumption: 2.23052 MiB (device 0)
2018-04-19 15:17:36.200 Iray VERBOSE - module:category(IRAY:RENDER): 1.12 IRAY rend stat : Material measurement memory consumption: 0 B (GPU)
2018-04-19 15:17:36.202 Iray VERBOSE - module:category(IRAY:RENDER): 1.12 IRAY rend stat : Materials memory consumption: 740.77 KiB (GPU)
2018-04-19 15:17:36.441 Iray INFO - module:category(IRAY:RENDER): 1.4 IRAY rend info : CUDA device 1 (GeForce GTX 1080 Ti): Scene processed in 26.655s
2018-04-19 15:17:36.445 Iray INFO - module:category(IRAY:RENDER): 1.18 IRAY rend info : CUDA device 0 (GeForce GTX 1080 Ti): Scene processed in 26.659s
2018-04-19 15:17:36.480 Iray INFO - module:category(IRAY:RENDER): 1.4 IRAY rend info : CUDA device 1 (GeForce GTX 1080 Ti): Allocated 830.853 MiB for frame buffer
2018-04-19 15:17:36.481 Iray INFO - module:category(IRAY:RENDER): 1.18 IRAY rend info : CUDA device 0 (GeForce GTX 1080 Ti): Allocated 830.853 MiB for frame buffer
2018-04-19 15:17:36.483 Iray INFO - module:category(IRAY:RENDER): 1.18 IRAY rend info : CUDA device 0 (GeForce GTX 1080 Ti): Used for display, optimizing for interactive usage (performance could be sacrificed)
2018-04-19 15:17:51.500 Iray INFO - module:category(IRAY:RENDER): 1.4 IRAY rend info : Allocating 1 layer frame buffer
2018-04-19 15:17:52.027 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Received update to 00001 iterations after 42.241s.
2018-04-19 15:17:52.715 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Received update to 00002 iterations after 42.928s.
2018-04-19 15:18:06.411 Iray INFO - module:category(IRAY:RENDER): 1.0 IRAY rend info : Received update to 00003 iterations after 56.625s.
How much system RAM do you have?
System 32Gig.
To confirm, you are sure that the card that is idling is NOT the one driving the displays?
If the card sitting idle is the one driving your displays, what is probably happening is the scene is hitting the cards vram limit. The card not driving the displays has more of it available, because the operating system will be reserving some, especially if you are on windows 10.
one way to test this would be to put a very basic prop into a blank scene and render it, and see if both cards get used
i know the log you posted makes it look like the other is being used, but it would be good to confirm
another thing you could do is use some other software other than task manager to see if that gives you the same information regarding the other card not being used. I use MSI afterburner to monitor temps, but it also shows you core and memory clock frequencies, which will jump to max when rendering
It's possible that both GPUs are actually rendering, and that Task Manager is misreporting GPU load.
I had the same concern: I added a second GPU, and during a test render Task Manager > Performance showed one GPU with light load (10%-40%) and the other GPU with zero load. I've seen similar weirdness when gaming on a single GPU: despite running a GPU-intensive game with the system fans screaming, I've seen Task Manager show surprisingly low GPU loads.
So I got a second opinion. GPU-Z is sort of a gold standard for reporting GPU information. It showed both GPUs running at between 99% and 100% of load. Interestingly, both Task Manager and GPU-Z seemed to accurately report the VRAM usage for both cards.
I ran a test render before and after adding the second card. In the same rendering time, the "after" test reached a significantly higher percentage of completion with about 1/2 of the iterations of the "before" test. So it does seem like both GPUs were active.
I did. Every driver after 391.35 has been this way. Revert to that one and your GPUs should both be used for Iray, but it has to be that one.
To truly see what your GPU is doing, use either EVGA PrecisionX or MSI Afterburner. It doesn't matter what brand your GPU is, both apps work on all brands. Either of these apps will report a wide variety of stats in real time, plus allow you to control the fans and do overclocking (BTW I suggest NOT overclocking a GPU used for Daz.) I like to use an aggressive fan curve to make sure the cards stay cool.
If the card is rendering, you'll instantly know. The clock speed will turbo, the fans should kick in, and the power levels will increase.
Whether or not your card works, I recommend using one of those apps to keep an eye on temps and things anyway.