Steve Smith talks about mixing and matching graphics cards for SLI.
Episode #8-06 released on October 1, 2017
First, you can't enable SLi between cards of different generations, and processor types. Meaning you can't enable SLi between a GTX 970 and GTX 1070. There do not have the same processor, and are not of the same generation. So, when asking if you can mix and match cards under this context, the answer is no. You can use both graphics cards in the same system, but you won't have any of the benefits of SLi.
Second, you can use two different graphics cards of the same generation and type. Meaning you can use a GTX 1080ti from Asus, and another from MSI. However, the way SLi works dictates that the weakest card is what the performance of both cards will have. You may encounter some weird issues using cards from two manufactures though, as power delivery and other factors will make them behave slightly differently. If you use two cards from the same manufacture then this should occur less, but same rule applies for performance, which will be based on the weakest of the cards.
Third, the best configuration, for anyone intent on having SLi, is two identical graphics cards. The performance, ignoring the silicon lottery, between the cards should be identical. Meaning that you will have the greatest benefit of performance, with a major caveat, not all applications or games support SLi.
For games and applications that do not support SLi, you can disable SLi specifically for those by visiting the Nvidia Control Panel, going to manage 3D settings, going to program settings, then selecting the program or game, going to SLI rendering mode, then selecting single GPU mode.
Host : Steve Smith | Music : | Editor : Steve Smith | Producer : Zed Axis Dot Net