Sli doubled my vram...

[da007255]

Hi

A while ago I bought myself a second GTX 970 4G from MSI. I plugged it in and configured the sli. Today I installed GTA V on my PC and went to the graphics settings. As I looked at the bar indicating the amount of vram left, I saw that my vram doubled. Normally I should see 4 gb, but I see 8 gb right now. Is that normal? I mean, I don't mind, but I'd like to know if it's a glitch or just something new in the latest nvidia drivers. Normally the vram should double, from my experience.

Regards

 

[da007255]

In my last sentence I meant to say that it shouldn't...

 

[SammChisnall]

Yeah if you're SLI'd then the 4GB from both 970's is shared along with the processing power, all games that support SLI/Crossfire will recognise the 8GB VRAM...or they should anyway.

 

[RCFProd]

VRAM doesn't stack. This is just a GTA V thing, and It's known for displaying that, however It's not correct and you still have only 4GB VRAM to use.

 

[rcald2000]

^ Agreed.

 

[SammChisnall]

VRAM doesn't stack. This is just a GTA V thing, and It's known for displaying that, however It's not correct and you still have only 4GB VRAM to use.

Does it not? god i've gone for years thinking it did. Well you learn something new everyday i guess!

EDIT: Does it work by both cards storing the same data in their VRAM and then splitting the processing between each card then? therefore keeping the same VRAM but improving processing power?

 

[RCFProd]

VRAM doesn't stack. This is just a GTA V thing, and It's known for displaying that, however It's not correct and you still have only 4GB VRAM to use.

Does it not? god i've gone for years thinking it did. Well you learn something new everyday i guess!

Nope. It might be in the future with DX12. But even then, people are not confident. [Link]

 

[13thmonkey]

VRAM doesn't stack. This is just a GTA V thing, and It's known for displaying that, however It's not correct and you still have only 4GB VRAM to use.

Does it not? god i've gone for years thinking it did. Well you learn something new everyday i guess!

EDIT: Does it work by both cards storing the same data in their VRAM and then splitting the processing between each card then? therefore keeping the same VRAM but improving processing power?

Your edit is correct, both cards need full access to all of the resources, and therefore whilst there is 8GB everything must be stored twice, therefore an effective 4GB.

Under DX12, if a game is coded for it, it will be possible to share the resources, BUT you then have to consider that the textures etc. need to move across the PCI-E bus to the card that needs them, this will take time, do I have it, no, where is it, over there, bring it over here then, now i have it, now i can use it, this has to impact performance.

 

[rcald2000]

+RCFProd +13thmonkey It's interesting, because I'm aware that DX12 is "supposed" to allow games to stack VRAM. However I've seen no confirmation or denial that it's actually working out that way in real life with native DX12 titles. Also, there are a lot of DX11 games that have DX12 wrappers, which I presume are definitely not stacking VRAM. I'm curious to find out what the conventional wisdom ends up being on this topic.

 

[sizzling]

A game being DX12 isn't enough. My understanding is this feature would need to be developed and built into the game itself. As far as I know no games have done this and I cant see many doing it, why waste all that development effort and then the need to support it.

 

[13thmonkey]

+RCFProd +13thmonkey It's interesting, because I'm aware that DX12 is "supposed" to allow games to stack VRAM. However I've seen no confirmation or denial that it's actually working out that way in real life with native DX12 titles. Also, there are a lot of DX11 games that have DX12 wrappers, which I presume are definitely not stacking VRAM. I'm curious to find out what the conventional wisdom ends up being on this topic.

It's a DX12 feature, which I presume means that it has to be specifically coded for, it's not inherent in DX12, DX12 just allows for it to be a possibility. Maybe this time next year...

 

[13thmonkey]

A game being DX12 isn't enough. My understanding is this feature would need to be developed and built into the game itself. As far as I know no games have done this and I cant see many doing it, why waste all that development effort and then the need to support it.

I think that singularity has enabled it, like they enabled mismatched multi GPU, but that's all I know of to date.

 

[RCFProd]

A game being DX12 isn't enough. My understanding is this feature would need to be developed and built into the game itself. As far as I know no games have done this and I cant see many doing it, why waste all that development effort and then the need to support it.

I think that singularity has enabled it, like they enabled mismatched multi GPU, but that's all I know of to date.

Yeah, Ashes of Singularity ''supports'' it. Works like crap though.