Problems with risers please help

[Statiksa]

So i have i7 4770k a Maximus VII Hero and a CX750M psu. I am trying to run 3 of the GTX 1060s

2 is running directly on the motherboard

I am trying to run 1 gpu on the riser.

On the riser where i have 1 gpu connected The gpu fans spin on the riser but the gpu is not picked up/detected on the pc/motherbord.

If i plug in just the riser alone and no other gpus the riser works and outputs video.

I have tried 4 risers all do the same different brands of risers as well were tested.

Any ideas? Thanks all info appreciated.

Please see pics of risers and setup here.

https://imgur.com/a/qtsqE

[gsarducci]

Try setting your PCIe slots to gen1 or 1x. You might be running out of bandwidth.

[malthrax]

Non-enthusiast-grade Skylake CPUs only have 16 PCIe lanes to the CPU.  The two GPUs plugged directly into the motherboard are running 8x/8x and using up all the lanes.  You'll need to move all three onto risers in order to free up bandwidth, unless you can set the slots to 1x in the BIOS.

That's my guess, at least.

[xxcsu]

with that setup you need to run all 3 cards from risers ... just like "malthrax" suggested erlier , you are using all your available pci lanes with that 2 plugged in vga cards ...