Dual video cards. How do you pick the primary one.

wayneheim · December 11, 2020, 04:58:07 PM

So I added a new rtx card to my machine and want to have keyshot use both cards but have Keyshot use the memory on new card but can't figure out how. Keyshot keeps using my old card as the memory choice. Someone said their was a setting in the nvidia control panel for primary card selection but I can't fine it. I'm not using an nvlink bridge because cards are not close enough.

Any thoughts?

Wayne

DMerz III · December 11, 2020, 07:31:21 PM

I don't have dual cards, so I can't test this, but when you turn on GPU mode and you go to GPU Usage (in the Ribbon UI), do you have the option to choose between your two cards there?

DriesV · December 12, 2020, 03:21:35 AM

If you have two graphics cards in your machine with different amounts of memory and use both in KeyShot, then the available memory will be limited to the card with the lowest amount of memory.
No way around that, unfortunately.

Dries

wayneheim · December 12, 2020, 10:11:17 AM

Yikes! That would have been a nice tidbit to know before I got a 3090 to pair with my older card. Funny thing, Photoshop uses the faster video card by default. Is this a keyshot limit? Something that can be added/fixed in later versions?

DriesV · December 12, 2020, 10:28:32 AM

As David mentions above, you can select the GPU(s) to use for GPU Mode through the GPU Usage dropdown. If you only select your RTX 3090, then you will have its full 24 GB of memory available. The GPU selection is remembered across KeyShot sessions.

The memory limitation is nothing new or KeyShot specific. It applies to all CUDA applications that use multiple GPUs.

Dries

mafrieger · December 12, 2020, 10:35:58 AM

Shouldn't it be possible to choose the 3090 for "Calculation" and the older one only to "draw" everything and output to the monitor?
Having the benefit of having the older card within this scenario taking the "drawing load "
- should free a little more memory for "calculation" (1-3GB) and
- the calculating 3090 does not have to switch between "calculating" and "drawing" which should make it a little faster (e.g. 5%)

wayneheim · December 12, 2020, 10:39:20 AM

I understand I can switch the 2070 off and just use the full memory on the 3090 if I'm loading a large model. Do you think the memory speed hit on the 2070 series vs the 3000 series is significant?

DriesV · December 13, 2020, 03:16:42 AM

The 3090 will eat the 2070 for breakfast, and dinner.
I honestly don't think it is worth combining those two cards for GPU Mode.

And as mafrieger mentions, you can set the 3090 as the only CUDA device in the NVIDIA Control Panel.
It does make sense to keep the RTX 2070 as a display-only card. That is, if your workflow doesn't require the actual graphics output capability of the 3090.

Dries