I know the board can do 4 way SLi with two 690 cards, but I have not tested if the board can do 4 cards in SLi. I will try and find out for you. There is another thread with similar problems to yours by the way. And I assume based on what you have said that you do have all the dip switched for the PCIe lanes on.
I sort of have in the back of my mind that if you put a card in the bottom slot then the others do not work. What happens if you only use three cards and do not use the bottom PCie slot?
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