Hey my setup is z97-deluxe with ozmosis i7-4790k 32GB RAM
my problem that I change video card from GTX 970 to Shappire r9 280x Trix
change dsdt for this video card
I have 2 monitors but only one working hdmi or dvi I can only work with one monitor 
maybe some one can help please
R9 280x Dual monitor not working
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Try to connect on of your displays with DP (maybe DP->HDMI adapter) and the other on with HDMI or DVI. I had the same Issue on my R9-270x and solved it that way.
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Thats probably not going to solve the issue but you can try.
I have the Sapphire R9 280x Tri-X OC myself. You need to set a framebuffer.
Do you have a defaults.plist? If yes then please set the framebuffer "Hamachi" and afterwards everything should be fine
Please do a NVRam reset after changing the defaults.plist!
