Noob question re: multiple GPUs

[pvl000]

Motherboard: ASRock Z97X Killer
GPU: 3x Radeon XFX RX 480
OS: Win 7 Pro 64
PSU: 1200W Gold+

I can run with any of the three GPUs in any of the 3 x16 slots without any problem.  Multiple GPUs are recognized in the BIOS diagnostics, but when I get to windows, anytime I have 2+ GPUs powered up none of them are recognized by either qtminer or ethminer.  They are also not recognized by the video settings program.  I've tried various combinations of bios and drivers.  Currently on stock bios and crimson 16.11.5.

I've tried the cards in another motherboard and had similar results.  I'm guessing I'm overlooking something really simple. 

Any suggestions?-

[ylpkm]

change pcie settings in bios if possible,
From auto to x8/x4/x4
and possibly the Gen setting from auto to Gen 3 for the 2nd and 3rd card. My motherboard gives issues if I put all 3 cards on gen 3, and doesnt see the other 2 cards on auto for the pcie interface setting (x16/x8/x4 etc)