Instal win 10, my 7xRX 480 works fine.
This helped!
Fresh Windows 10 installation and all 7 GPUs able to run even without 6xGPU MOD! I can't believe how much time I lost trying to get 5+ GPUs to run on Windows 7...
Thank you
batko and
lbr for help!
Now I "just" need to resolve stability issue of 6th and 7th GPU, which crash always after 5-6 minutes of mining.
Did you try modifying the bios? set PCIE ports to gen 2, choose the 8x 4x 4x option, deactivate integrated audio port, update bios, and connect the screen to the first 16x port.