ASRock 970 Extreme 3 and not more than 2 7950s running

[Igotcha]

Hi,

I try to run 3 x 7950 on my ASRock MB with riser cables.

Two cards run fine on the two PCI-E x 1 slots but when I try to add the 3rd card on a PCI-E x 16 or in the PCI-E slot on the board the PC isn't booting anymore.

It seems that the PCI-E x 16 slots are not recognized.

Do I need a powered PCI-E x 16 cable or is there something else I can setup in BIOS or on the board itself?

Edit: I have a 1.200 PSU, so that shouldn't be the problem.

Thanks!

[Igotcha]

I quick built me a powered riser cable and it works now.