I've a Mac Pro 2013 with two AMD FirePro D700 graphic cards.
With Boot Camp I can work with Mac OSX and Windows 8.1.
I've bought a new LG display (38UC99-W). With MacOSX it works excellent. Refreshrate 75Hz at 3840x1600px.
But under Windows 8.1 the refreshrate was max. 30Hz at 3840x1600px.
So I thought I'll update the driver of the AMD graphics cards. After install the Apple Boot Camp software graphics driver (AMD-website) I can't control the graphic cards anymore. In device manager the display adapters are disappeared.