Hi, Just bought a new graphics card, EVGA Nvidia Geforce GTX770. I have no OS on my Mac PRO 3.1 How can I install OSX and how can I install GPU driver. I tried to install OSX on a USB external SSD but the Mac is not booting up. I just have a black screen. This is a non-flashed GPU. And by the way...how can I flash my graphics card in 2017? Because tools for flashing in no longer supported by developers. Thank you!