Gtx 970s in sli

[Guest]

Anyone who can answer, I was thinking about upgrading to sli 970s in the future (I currently have 1). I understand that the vram doesn't stack, which might change in dx12. But my question is that if the gtx 970 goes over 3.5 gb and actually reaches 4, will it then be able to use the other 4 gb on the second card in sli? When I hear "stacking vram" in dx12, my understanding is that it means it has the capability to use the prioritized 3.5 gigs of vram from both cards first before it goes into the last gigabyte. Is this correct or is the lack of stacking vram support in dx11 and previous versions mean they can't stack at all and can only use the vram from one card?

I was going to be running the 970s in 1440p. That's the plan anyway, and with 3.5 gb could be a problem on more demanding games in 1440p.

 

[Xtergo]

http://www.youtube.com/watch?v=jPlCIUh_Tp0

 

[Zyb3r]

Hello

The stacking of VRAM with DX12 has everyone confused at this stage. VRAM currently does not stack because the GPU vendors have to support it in there drivers and the games also need to support it.

You ask that if you use up your VRAM on one card if it will move over to the next? Unfortunately no, it does not. That is not how SLI works. Both GPUs render frames yes, but the data is basically duplicated onto both cards. Card 1 will for example render frames 1, 3, 5 etc and card 2 will render 2, 4, 6 etc.
You basically get double the performance, but the memory will still be a limiting factor.

I think it will be a while before we see stacking of VRAM happen successfully.