Mac OS X boot screen blackout

[Cpoor]

I have a 2009 Mac Pro flashed to 5,1 with 2 Xeon 5690, 64gb ram , Ge Force 680 4 gb flashed w/ Mac boot screen. I am running 10.11.2, and the latest nvidia Mac driver. There is one cal digit USB 3.0 esata pic-e cardconnected to the OS X boot drive.y
When the dvi cable is connected to the DVI-I port, the boot screen stops half way through, and quits.
The Windows 10 drive boots normally off the same port while holding down the option key.
The OS X drive boots normally off the DVI-D port.
Any thoughts?

 

[Fl0r!an]

Thats normal behavior, your card will lose one DVI port when flashed with this ROM.

 

[Cpoor]

Thats normal behavior, your card will lose one DVI port when flashed with this ROM.

Thanks for you input.
Will the displayport function normally, and why is Windows supported on that same DVI-I port?