Oh then I should buy and try with the mobo BTC-PRO and buy USB Power Riser,

What about the Dummy Plug ? No one say something.

Oh thx for your answer you help much ! Maybe its just about the mobo. Thx all

When I said rise cable with molex connector I means power riser. So yes I got it. I Check for in Google to find problem with the motherboard but difficult to find who have the problem. So maybe I need to change motherboard but the motherboard have 5 port x 1 and 1 at 16x. Normaly it have to work no ?

Hello,

I have some hardware problems to connect all my card recognized by the system ( Windows 8.1 Pro/Core ).

Only 2 have been recognized, one time it's work with 3 card.

Here my hardware ;

ASRock B85 Anniversary
Intel Pentium G3258 (3.2 GHz) FSP AURUM 1200 Pro 80PLUS Gold
 + with an other power supply  850W --> Connected in syncro with ADD2PSU
Corsair Force Series LS 60 Go
G.Skill NS Series 4 Go DDR3 1333 MHz CL9

Graphic cards :

6 X AMD SAPHIRE RADEON 290X
 
5 connected with a cable Riser PCI Express 1 x to 16x with molex connector

1 connected with a cable Riser PCI Express 16 x to 16x with molex connector

Drivers is installed.
Motherboard graphic integred is desactived.
The rig can run 6 graphics card with Windows 8 but don't recognized 4  or 3 of them. The problem is when I change from the port with the cable riser
Its change all time to where I have to put the cable for my monitor from the port 1X ! Also the 16x to 16x never recognized by the way.

Maybe I should try dummy plug on all my card because the motherboard is not MULI-GPU ? Or change the cable riser to buy a more expensice, the one with USB ?

Please if someone who knows what I have to do for the next. Thanks.