Poor performance GTX 1080's in SLI or MGPU

from AshesoftheSingularity Forums

Hi all, 

It's pretty strange with every on here saying how their performance is much better when switching off SLI and running MGPU in Dx12. When I do this I lose around half the performance I have using a single GPU.

Currently running a single 1080 is around 10-20 FPS increase for me, both in Dx11 and Dx12. I wondered if this was just down to Nvidia driver's being poor for the 1080's however it seems plenty of reviewers are managing to at least run Ashes using SLI or MGPU to net the same FPS or slightly more than with a single card. I can't see any reason why I'm actually losing FPS and to top it off feels very choppy.

 

I wondered if anyone else with 1080's in SLI is having the same issues or am alone on this? Plus anyone who think's they have a fix, I'm all ears. 

 

Thanks in advance.

9,417 views 3 replies
Reply #1 from AshesoftheSingularity Forums Top

What are your CPU and RAM? Running in mGPU needs 16GB of RAM and it is also more demanding on the CPU. So perhaps with a less than high end CPU performance could be worse? Just speculation.

Reply #2 from AshesoftheSingularity Forums Top

Hi, 

I'm running a i5-4670K at 4k and 16 gb of ram at 1600mhz.

Is that enough you think or is the CPU letting the side down?

Galactic Civilizations III
Reply #3 from AshesoftheSingularity Forums Top

That is not a bad CPU, it might bottle neck things a bit for 2x1080s but losing 10-20 FPS in mGPU mode seems a lot, but who knows, with 2x1080s a huge amount of stuff going on. 

How is your RAM configured? It seems to make a really big difference in this game. Do you have 2 sticks but 4 RAM slots? If I am remembering correctly to take advantage of dual channel in that kind of configuration the cards should not be side by side, but in slots 1 and 3 or 2 and 4. Check with your MB manual. If you have 2 sticks and 2 RAM slots then you can ignore me. :)

(here is a link to the Steam forums with a couple of 1080 owners talking about RAM and performance, perhaps the DDR4 RAMs higher bandwidth is a big help)

http://steamcommunity.com/app/228880/discussions/1/358415206091503844/

There was another thread where a 1080 user or 2x1080 user overclocked their RAM too and got a significant improvement but I can't find it. So overclock RAM and CPU? :)

 

Have you tried testing at 1080p instead of 4K? Normally the lower the resolution the greater the chances of a CPU bottleneck while with a high resolution the greater chances of a GPU bottleneck. If you try this at 1080p or 1440p is the FPS reduction even worse relative to 1 card vs 2?