2nd GPU advice

Magic Man

I'm using a RTX3090 but am considering adding in my old GTX1080 to use additional monitor outputs for other uses.

Would enabling CUDA rendering on the 1080 (8GB) limit/hinder rendering on the 3090 or would it be better to disable the 1080 from the rendering options?

onix

no there is no reason to disable 1080  as it may add some extra performance. it will get automatically disabled if you will have some bigger scene that does not fit in 8GB GPU

but if you are concerned about memory and maybe some sm, all performance penalty, you should leave all monitors on just one GPU rather than spreading them on both unless you need more than 4 monitors because if you connect the monitor to the GPU windows automatically will reserve 1GB on that GPU making it unavailable.

anyway, I think 1080 will have pretty low performance in comparison to 3090 so using it may be insignificant to the total performance  and it is unclear if your power supply will be able to power both cards at the same time on the full load

PerttiA

onix said:

but if you are concerned about memory and maybe some sm, all performance penalty, you should leave all monitors on just one GPU rather than spreading them on both unless you need more than 4 monitors because if you connect the monitor to the GPU windows automatically will reserve 1GB on that GPU making it unavailable.

Does not matter if there's monitor connected or not, the VRAM will still be reserved unless using TCC driver, which according to tests here at the forum isn't really an option with the consumer models.

YannosBark

Not being matching GPUs, no option to do SLI. I have found that dual non-conformed GPUs 

actualy degrade performance because the two will cross vie for both time sync and pipeline operations.

with conformed (matched) but no SLI, there is a slightly better situation than above, still there will

be some battling.

conformed, SLI, is really the only wise path I've found.

onix

PerttiA said:

onix said:

but if you are concerned about memory and maybe some sm, all performance penalty, you should leave all monitors on just one GPU rather than spreading them on both unless you need more than 4 monitors because if you connect the monitor to the GPU windows automatically will reserve 1GB on that GPU making it unavailable.

Does not matter if there's monitor connected or not, the VRAM will still be reserved unless using TCC driver, which according to tests here at the forum isn't really an option with the consumer models.

 

I can't guarantee it but it was an issue in early windows 10 version now as I know it was fixed and memory is reserved only if you connect the monitor to the video card, Microsoft was receiving quite a lot of complaint on that matter. (I didi not test that myself yet)

 

PerttiA

onix said:

PerttiA said:

onix said:

but if you are concerned about memory and maybe some sm, all performance penalty, you should leave all monitors on just one GPU rather than spreading them on both unless you need more than 4 monitors because if you connect the monitor to the GPU windows automatically will reserve 1GB on that GPU making it unavailable.

Does not matter if there's monitor connected or not, the VRAM will still be reserved unless using TCC driver, which according to tests here at the forum isn't really an option with the consumer models.

I can't guarantee it but it was an issue in early windows 10 version now as I know it was fixed and memory is reserved only if you connect the monitor to the video card, Microsoft was receiving quite a lot of complaint on that matter. (I didi not test that myself yet)

It isn't that long since it was tested, maybe a couple of months ago and I think it was in this thread somewhere;

https://www.daz3d.com/forums/discussion/341041/daz-studio-iray-rendering-hardware-benchmarking/p1 ;

Magic Man

Many thanks all

ebergerly

For info, I have a GTX-1080ti and an RTX-2070 Super running on my machine, and the GTX-1080ti runs my 3 monitors. Attached is a screenshot from Task Manager showing DAZ Studio while doing an Iray render on both cards. I also had Blender open but doing nothing.

You can see that the big users of GPU VRAM are (far right column):

-  DAZ Studio, which was using 4GB in each GPU for the render for a total of 8GB; 

-  Blender, which was using 330 MB doing nothing, and

- dwm.exe (Windows 10 Desktop Windows Manager) which is the W10 process which manages your desktop and allocates some of your GPU VRAM to do its job. You can see that DWM is using less than 300MB across the 2 GPU's. 

So yeah, adding a 1080ti should be fine.