Thank you so much man! I finally solved it!
What I did was:
1. Flashed my bios with the latest rom
2. changed bios settings (enable UEFI mode)
3. run a new windows setup (cleaned and converted ssd to gpt before the installation)
4. installed latest amd drivers (patch wasn't needed!)
5. went back to the bios settings and enabled 4G decoding and done!
hey buddy, I'm having the same issue with same cards and same mother... I tried your steps but it ends up with windows not load up and crashes when I use 6 cards at same time with 4g setting enable.. windows loads in 5 cards but still having that 5th card not working... 4 cards windows load and 4 cards working good.
I skipped the installing new windows step and converted my ssd to gpt then turning on UEFI mode... did I done something wrong? also which windows you are using.
will appreciate if you help me...