4 way sli on 3 way capable mobo with 4 pci-e slots

[Siegehammer]

I have a question I can't seem to find the answer for anywhere. I have a p9x79 pro board & it officially supports 3 way sli. It has four pci-e slots one of which is connected through the south bridge. If one were to connect four gtx680 cards via pci-e ribbon cables eliminating the spacing issues of the slots, would 4 way sli be possible?

 

[andybird123]

the spec sheet says that it supports quad-fire, but only 3-way SLI, which is odd, every other X79 board I can find that has 4 slots states 4 way sli support...

 

[Siegehammer]

the spec sheet says that it supports quad-fire, but only 3-way SLI, which is odd, every other X79 board I can find that has 4 slots states 4 way sli support...

Well it might either be because cards for 3/4 way sli tend to be dual slot leaving no space for a 4th card or because SLI can't run on a S/B connected PCI-E slot (adds lag).

 

[andybird123]

but both of those reasons would apply to quad-fire as well
it might just be that the southbridge only supports crossfire (you can also get around cards being dual slot by watercooling, so I wouldn't have thought they'd put that forward as a problem)

 

[Siegehammer]

Usually Quad is 2x dual GPUs (GTX690 or HD6990) whereas 4 way is four single GPU cards but then I don't know if 4 way crossfire is also just referred to as quad to simplify marketing.

 

[Mr. May]

The 6xx series will always be due slow even if you water cool them due to double stacked power connectors and double hight I/O plate unlike the 4 and 5 series could make them single slot on water

 

[Mr. May]

As for the four way try just running sli thought the slot In question before you waste your money

 

[Siegehammer]

Tried it (took some time due to my water cooling) & indeed SLI works on the PCI-E slot that runs through the south bridge. So I'm pretty certain now 4 way should work but all cards would need to be connected via PCI-E ribbons since there would be no space for four dual slot cards on the mobo but this would save money on replacing the board.