Guys, Need some help getting my non-EFI flashed ASUS GeForce GTX 780 (display port, HDMI, DVI connectors) working in my system. My display in an 30" Apple HD Cinema with DVI Connector. My system is on OSX 10.9.5, CUDA version 6.5.18, NVIDIA web driver 334.01.03f01. Power to the card: It is plugged into slot 1 (x16 PCI-E slot), and I plugged in my existing 6pin cable to the 6pin port of the card. I purchased an external power supply- a Thermaltake 500W, to deliver a PCI-E 6+2 pin to the 8 pin port on the card. System boots just fine with my ATI HD 5770. When I swap out with the ASUS GTX780, I hear the chime the system has booted, I wait 10 minutes but my screen is still dark. I move my DVI connection from one connector to the other on the GPU card, but still my screen stays dark. I know the GPU is receiving power from the external PSU as it has indicator lights that go green when power is on, and red when power is off at the 8pin connector. I also moved the GPU to slot 2 and it still exhibits the same behavior. I have an older GT120 as well, and I booted my system with it (slot 4- as it only requires power from the PCI-E slot) and the ASUS GTX780 (slot 1). When I go into About This Mac, System Report, Graphics/Displays- only the GT120 is shown. Same thing with System Preferences, NVIDIA Driver Manager, ECC only shows the GT120 connected in slot 4- slot 1 displays "No Device Found". I don't know what else to do at this point- any pointers in the right direction would be greatly appreciated.