SLI Questions

My son is going to be buying a new custom computer soon. He will have a GTX980 4gb video card in it. I have an old card laying around, a GTX 275 896mb. Both have PhysX. My question is, can these be run in SLI or will it not work? If it will work, how will it affect performance? And can the 275 be used as a dedicated PhysX card? Thanks for the advice.

Edited by Optimystic - 14 Feb 2015 at 9:20am

Bpratt beat me again. I don't think he ever sleeps.

As he said the GPUs must match.

A good alternative might be 2 GTX970 in SLI.

I don't think the 275 would do it for a PhysX card. (along with the power of a GTX980)

From the Nvidia site: (because thinking hurts and it's easier to copy than type. )


[[
Which NVIDIA GeForce GPUs support PhysX?
The minimum requirement to support GPU-accelerated PhysX is a GeForce 8-series or later GPU with a minimum of 32 cores and a minimum of 256MB dedicated graphics memory. However, each PhysX application has its own GPU and memory recommendations. In general, 512MB of graphics memory is recommended unless you have a GPU that is dedicated to PhysX.

How does PhysX work with SLI and multi-GPU configurations?
When two, three, or four matched GPUs are working in SLI, PhysX runs on one GPU, while graphics rendering runs on all GPUs. The NVIDIA drivers optimize the available resources across all GPUs to balance PhysX computation and graphics rendering. Therefore users can expect much higher frame rates and a better overall experience with SLI.

A new configuration that’s now possible with PhysX is 2 non-matched (heterogeneous) GPUs. In this configuration, one GPU renders graphics (typically the more powerful GPU) while the second GPU is completely dedicated to PhysX. By offloading PhysX to a dedicated GPU, users will experience smoother gaming.

Finally we can put the above two configurations all into 1 PC! This would be SLI plus a dedicated PhysX GPU. Similarly to the 2 heterogeneous GPU case, graphics rendering takes place in the GPUs now connected in SLI while the non-matched GPU is dedicated to PhysX computation.
]]

As stated there is good and bad in using a dedicated PhysX card. For the most part, set-up and drivers has to be near perfect or PhysX will be spit between the dedicated card and other GPUs which is a problem.


Edited by Pacesetter - 14 Feb 2015 at 9:59am

Thanks for the info. The gtx 275 has 240 cuda cores and 896mb of memory. Wouldn't that be enough? My main concern would be it's pci-e 2.0 bus. His mobo will be the GIGABYTE Z97X-SLI

Generally, yes, the GTX 275 would do it. However, what I am seeing in games I play and beta test is that PhysX takes a major hit and can get to over 1G GPU ram used for short periods of time. This and the fact that games are increasing upgrading the graphics, detail ( fire - smoke particles - spell detail, etc) is the reason for my statement.

For me, I'd SLI 2 970s or 980s. There is a game I am invited to beta test that actually suggests a minimum of a 650Ti card and 770+ in SLI is recommended. This one will be super graphics intensive.