SLI gtx 770 with gtx 970?

[Ike0]

Is it possible?, it is only a bit more than a 770 but substantially better

 

[Novuake]

No, not possible.

 

[Eli Little]

No, this is not a possible configuration. When it comes to SLI or Crossfire, you can only SLI two GPUs if
ONE; they have the same GPU. So for example you can only SLI a 770 with another 770, since they are the same GPU (Graphics Processing Unit). You could not, however, SLI a GTX 760 with a GTX 780.
SECOND; they must have the same amount of dedicated video RAM. So, you could SLI your 770 with another 770, but it must have the same amount of RAM. So if your 770 has 4GB of VRAM, you MUST SLI with another 770 with 4GB. You can not SLI with a 770 with 2GB of VRAM.
And THIRD, you need both a GPU and a Motherboard that supports SLI. For GPUs, the manufacturer must say that the card supports the use of an SLI bridge. If the manufacturer does not say that a card can be SLI'ed, than it CANNOT be SLI'ed no matter what you do. For the motherboard, make sure that it has at least TWO PCIe x16 slots. If it does not, than there is no way to SLI two cards. This goes for triple SLI as well, with at least THREE PCIex16 slots. In case you don't know, this is what one looks like.

After you have made sure that all of these things are the way they need to be, THEN you can SLI. For reference, these are cards you can SLI-

2GB VRAM- http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007709%20600451260%20600007782&IsNodeId=1&name=2GB

4GB VRAM- http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007709%20600451260%20600007787&IsNodeId=1&name=4GB

 

[Cynystyr]

Eli's answer is mosty correct. You can SLI two cards with different VRAM (video memory), but it will only run at the lower memory. So a 4GB card and a 2GB card will down-scale to 2GB. This is the same for the speed of the cards. Two GTX 780's with different speeds in SLI will down-scale to the capabilities of the slower card.

 

[Eli Little]

Actually that is incorrect. Here, this LinusTechTips video sums it up nicely-http://m.youtube.com/watch?v=cxc6cb3_y0w

 

[acer0169]

Just thought it's worth pointing out that you can SLI two completely different cards. Some work, some don't. I read it a while ago. SLI and Crossfire are pretty much all software based. If you get a motherboard that says it's crossfire only and doesn't support SLI, you literally just need to download HyperSLI and you can run SLI no problem.

Same with different cards, there are many documented computers running two cards. You can read it here:
http://www.techpowerup.com/forums/threads/sli-with-different-cards.158907/

I've seen people running their old card with their new upgraded card without issue.