Pascal only supports 2 SLI
There are new details on Pascal architecture ( coming with the new Nvidia GTX1080 and 1070 ).
Pascal only supports 2 SLI cards which means you will not be able to use more than two 10 series graphic cards simultaneously. Even though there is no official statement about the topic from Nvidia, pictures posted by EVGA supports the news. Each Nvidia GTX1080 has two different SLI bridges.
Also, it is not clear why Nvidia chose to limit the number of Sli bridges.
Source – ShiftDelete.net