Multi-GPU Rendering - Mix Graphics Card

[astrocom]

I am new to GPU Rendering but now that I have a copy of V-Ray for modo I'd like to try to use more than one Graphics Card.
Currently I have a GTX 980 Ti installed in my PC and for the second card:
1) If I were to add another GTX 980 Ti must the second card be identical to the existing one (not trying to SLI) or can I use a different GTX 980 Ti from a different manufacturer?
2) Can the second card be a different GTX, for example a GTX 970 or GTX 1070 or GTX 1080? I know it could mean the system would only utilize the lesser of the two graphics memory but can I set the slower of the two to drive my display and the faster one to rendering?
3) or Must the two card be of the same generation (i.e GTX 980 Ti + GTX 980 Ti, GTX 1070 + GTX 1070, GTX 1080 + GTX 1080, etc).
4) Any other important info I should know?

[vladimir.nedev]

1. You can use a different one.

2. Yes it can be a different architecture, as far as I know, and you are right about the VRAM.
I have this setup on my PC - for display I have 560Ti, which is Fermi architecture with only 1 GB of VRAM, for RT GPU rendering I have Quadro M5000, which is Maxwell architecture, with 8GB of VRAM.

3. No need for them to be the same generation.

4. Take a look at the docs : https://docs.chaosgroup.com/display/.../GPU+Rendering

If, you are on Windows 10, you might run into some trouble selecting the devices, see here : http://forums.chaosgroup.com/showthr...-device-to-use

Greetings,
Vladimir Nedev

[astrocom]

Thanks Vladimir for the quick and detailed response.

"I have this setup on my PC - for display I have 560Ti, which is Fermi architecture with only 1 GB of VRAM, for RT GPU rendering I have Quadro M5000, which is Maxwell architecture, with 8GB of VRAM."
==> I assume for your rendering V-Ray would be able to Utilize the complete 8GB of VRAM from your Quadro M5000? I thought the bottleneck would be the slower of the 2 cards?

Does this also mean that for not so very large or complicated scenes since I am mainly doing product rendering and not really any Archvis, it makes sense to have a set up like yours with the card for handling display to have the minimum VRAM? It would be a waste if I add a GTX 1080 with 8GB for the rendering and leaving my GTX 980 Ti with 6 GB for driving the display since I don't expect my product scene setup to exceed 8GB; isn't it?



Daniel

[vladimir.nedev]

I assume for your rendering V-Ray would be able to Utilize the complete 8GB of VRAM from your Quadro M5000? I thought the bottleneck would be the slower of the 2 cards?

If only the Quadro M5000 is used for RT GPU, then 8GBs are available for RT GPU, yes.
If both are used, I am not sure what happens if the scene exceeds the 1 GB of the smaller card.

It would be a waste if I add a GTX 1080 with 8GB for the rendering and leaving my GTX 980 Ti with 6 GB for driving the display since I don't expect my product scene setup to exceed 8GB; isn't it?

I don't understand what you mean here.

Greetings,
Vladimir Nedev

[astrocom]

Thanks again Vladimir.
Your first answer sort of also answered my second question.


Daniel