Hi All,
 
I am trying to make 4 1080TIs work with x299 dark. The processor is i9-7920x with 44 PCIe Lanes.
I can't get x16 to work with single gpu on any PCIe slot.
Slot 6 only works at x4 on PCH, cant get anything else to work there not even with single GPU and on CPU lanes.
Slot 1 only works at x4 in single GPU config.
Slot 2,3,4 work on x8 with single GPU.
 
I could get 3 GPUs to work, x8 on slot 2, x8 on slot 4, and x4(PCH) on slot 6.
If I plug another gpu on slot 1 with above configuration, I only get slot 2 and slot 6 GPUs to be detected, slot 4 is no longer detected.
 
Also, I have evo 970 NVMe drive on m2 slot 1, which I have tried with and without in all configs. It changes nothing.
 
Was wondering if I could get some support on this issue. I need to get all 4 GPUs to work together.
 
EDIT: I have updated to BIOS 1.09, have also tested 1.08.

What He Said ^
With 3 or more Graphics Cards + M.2 you will NOT see any Graphics Cards @ x16.
A Must "Supplemental PCIe 6-pin Power Connector"
You will need to Remove your "EVO 970 NVMe drive on m2" for 4 Graphics Cards.
I could get 3 Cards to work but not a 4th Card with my EVO 970 NVMe Drive on M.2 installed.
With 3 Cards I got X16 - X8 - X8 with 4th card I got x8 - x8 - x16 - x8 (No M.2)
As shown Below (But Disable the Last 2 that I show Enabled)

 
Check here as well, yours should also look like the below Image.

 
Make sure you have all the items below set to Auto or all set to GEN3
If you cannot see all 4 Cards here in the Bios then a settings is blocking the 4th. This Screen as well as the Upper Right Corner.