Guys,
I'm having a hard time getting my new rig to boot

MOBO: Asrock H81 Pro BTC
GPU: 6 x Rx 480 Sapphire Nitro 4Gb
PSU: 2 x Corsair 850 W
OS: Win10 x64
I have two molex connectors powering the mobo with extra juice and I'm not using powered risers.
Everything was running great with the previous video cards (R9 270) but now I can only get the mobo to boot with 3 video cards, and one has to be directly connected to the 16x PCIe.
Isn't it strange? I have extra power available and besides, the old video cards were consuming more power than these new ones.
Any ideas?
Change UEFI settings? Anyone messing with the Gen1/Gen2 setting?
Anything else?
I have another 6x480s coming soon!
Any help will be greatly appreciated

Thank!
C'mon guys, a lot of you are using the 480 + H81 BTC Pro.