Please help: 2 of the 4 290X are way too slow when performing dictionary attack

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Right, I just had that idea when he said that he's using 2 different brands, 2 times ASUS and 2 times Sapphire so I thought maybe the Sapphire (or the ASUS) are fake ones.

I just had an idea. Why not switch the ASUS and the Sapphire, so that the ASUS are connected to the risers and the Sapphire on the board. If it's the riser card or the 1x, the speed should be roughly the same (I mean the drop of card #3 and #4)