Make sure you select in BIOS x6 GPUS
Where is this option in Bios? I couldn't find it! I am using Biostar TB-250 BTC
There isn't that option. Go into chipset and enable mining mode. Then go to the one below onboard devices, in there you see PICE management, go there and set all 1x PCIE to Gen 2.
All of these options has been done before (before was Gen 1 and now changed to Gen 2). But fifth GPU driver is still not installed in device manager.