New USB 3.0 cords do not solve problem. New risers arriving tomorrow, and a new MB the day after. Will update if any of this solves the problem. If not, I likely have a bad MB.

My BIOS is updated (assuming the internet flashing utility actually functions). I have tried 3/4 of the 1x slots and nothing. I have tried every slot of the PSU and it isn't the problem. Whichever GPU is plugged into the 16x slot shows up in device manager, none of the others do.

I don't have access to another desktop, but the cards all work in the 16x slot. The integrated graphics works okay. My problem is that the only known good slot is the 16x.  I'll try the memory stick trick.

I think I will call ASRock tomorrow to try to get a new MB. Thanks for the help.

I’ve been mining crypto for a few months without a problem. A 1 GPU system isnt really worth the inefficiency so I decided to upgrade. I got a good price on two more RX470s and a GTX1070. Here is my current functional setup:

MB: ASRock H81 Pro BTC R2.0
CPU: Intel Pentium G3260
GPU: Sapphire Radeon RX470
RAM: 1 x 8gb stick of some kind
PSU: Corsair AX1200i
HD: Intel 180gb SSD
Risers: Powered -- 6 x eBay (SATA connection), 2 x local vendor (Molex connection)

I have tested each of the risers and GPUs successfully on the 16x PCIE slot and they all work. I have an HDMI cord plugged into the 16x slot (whether or not there is a riser this works). This leads me to believe that the problem has something to do with the MB and not the risers themselves. Here is what I’ve tried:

•   Removing the MB battery
•   Resetting CMOS (many, many times)
•   Disconnecting SSD
•   Using both and only one of the MB 4-pin molex power connectors
•   Both Linux and Windows 10 to rule out OS problem
•   In BIOS:
           o   Changing PCI to Gen1 from Auto
           o   Choosing PCIE as default instead of onboard
           o   Disabling IGPU
•   Dummy HDMI in GPUs attached to 1x risers
•   Everything is plugged into the proper spot on the PSU
•   Same processes on GTX1070
•   Installing several different versions of AMD drivers including the mining edition

Question:
•   Is it possible that different risers of USB 3.0 cords could fix my problem?
•   Do I need to jump the 1x slots?
•   Anything else I haven’t tried?

The fan on the GPUs that arent recognized don’t spin, but the unit heats up.

Tl;dr my risers all work fine in the 16x PCIE but don’t work in the 1x despite the trying the bulleted suggestions and therefore cannot get more than 1 GPU recognized on my rig

Please excuse the rat’s nest of cords.

Thanks for the help