A little prehistory.
Hardware:
Gigabyte H110m-D3A, bois 23, CPU is G3900, ram 4 gb. Windows 10 64 bit. PSU is 500W corsair and server power supply 1200W.
Running 2 R9 280X for 3 weeks.
Suddenly the rig started to restart and i found that the PSU is the problem.
I bougth fortron he-500. I connect the psu to mainboard and cpu and hdd and one R9 280X. The windows did not detect anything in device manager. Any of the cards. I bougth 4 more R9 280X. /My plan was to use 6 vga card on the same board/
What i tryed:
- BOIS restore, flash to latest and many bois setting variants - not detected any card
- Fresh install of Windows to other hdd - not detected any card
- install of different AMD drivers 15.20,15.7,16,17 and uninstall every time with DDU - not detected any card
- try to plug any of the 6 gpu card in pcie16 line - not detected any card

I need help on troubleshooting. Can`t imagine what else to test.
Thank you for the support!