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2xGPUs & PCIe lanes

PostPosted: Thu Jul 19, 2018 9:50 pm
by Paul Draper
Any advice please? I can't seem to find this in the config guide.

If I have two identical GPUs (1080Tis in this case) how would Resolve be if one were installed on a 16x PCie bus, the other on a 16x (electrical 4x)? Would likely set that up as one GPU only for the displays, the other for compute only & the first also as 'use display for compute'. Any downside to Resolve performance benefits with that config?

I 'could' move things around to accomodate 2 x identical 16x PCIe buses, but presently I have a thunderbolt card installed which requires the use of one particular PCie slot, hence the limitations.

Thanks.

Re: 2xGPUs & PCIe lanes

PostPosted: Thu Jul 19, 2018 10:04 pm
by Andrew Kolakowski
It would be better if you could have both card running at x8.

Re: 2xGPUs & PCIe lanes

PostPosted: Fri Jul 20, 2018 3:00 am
by Paul Draper
Thanks, no idea why that might be. However, I only have x16 & x4 slots.

Re: 2xGPUs & PCIe lanes

PostPosted: Fri Jul 20, 2018 3:51 am
by Carsten Sellberg
Hi.

If you mount dual GTX 1080 Ti's in your Precision T7910 will you want to use the two x16 slots.
So I will prefer to ask you what Thunderbolt card you are using. And look into why it is required to be in a certain slot?
May be it is so simple that the cable to the header on the motherboard is to short?

Regards Carsten.

Re: 2xGPUs & PCIe lanes

PostPosted: Fri Jul 20, 2018 4:17 am
by Paul Draper
Carsten Sellberg wrote:If you mount dual GTX 1080 Ti's in your Precision T7910 will you want to use the two x16 slots.
So I will prefer to ask you what Thunderbolt card you are using. And look into why it is required to be in a certain slot? May be it is so simple that the cable to the header on the motherboard is to short?


Interesting, thanks for this. Yes, now seems clear that as you say, all that will happen is Resolve will run both GPUs at the speed of the lowest & that is quite clear in the config manual, albeit stated in a different way.

The idea about the location of the TB card is intriguing and will look into that with Dell. In my experience, is not unusual for TB add-in cards to be pre-allocated a specific slot by the manufacturer. But the idea about the cable and header may well be a very possible solution. It would also solve a bunch of other card slot orientations if the TB card could be placed in another location; 7 slots on this machine.