NVLink with 2 cards, the rest without

[Nejc Kilar]

Hey everyone,

I didn't want to derail any existing topics so I opened a new one, hope thats ok.

Would really appreciate some help understanding whether a configuration of say 2x2080 + 4x 2080tis can work with NVLink on those two 2080s?

So basically, the 2080s would have 16GB via NVLink and the 2080tis would be just normal 11GB. Since NVLink is basically an extension of SLI driver wise (for the Geforce series at least) I'm wondering whether that configuration could even work. Anyone tested it perhaps?

Thanks in advance!

[matanov]

Hey,

Yes, this config will run but capped at 11 GB (the card with the smallest amount of VRAM).

It will be really important the CPU to be powerful enough to not bottleneck these 6 cards.

[Nejc Kilar]

Slizer, thanks for chiming in, I appreciate it

Actually I have a chassis for a total of 10 GPUs but 4 of those will potentially run in an x4 mode via a x16 splitter. Otherwise we are looking at a dual Xeon build with 80 lanes.

Are the PCI-E lanes the CPU bottleneck you are referring to?

[matanov]

No, there is a lot of actual work done on the CPU (like feeding the GPUs with tasks). The only benefit from x16 will be probably on interactivity.

[Nejc Kilar]

Gotcha. I suppose its a long shot to ask but have you tested or heard from any customers how much (if any) of a bottleneck something like a 72 thread Xeon might be?

[matanov]

A 6 cores / 12 threads CPU on a very high frequency will be enough for 6 GPUs

[Nejc Kilar]

Perfect! Thank you for sharing the wisdom

[Nejc Kilar]

I'm back with a bit of an extra question if you don't mind Does SLI / NVLink work even if the 2080s wouldn't be GPUs 0 and 1? Aka if I use the 2080ti to drive the screen and the 2080s get dummy plugs. Anyone has any experience with that sort of thing?