I own a Mac Pro 5.1 that I swapped out the original ATI HD5770 for a new Nvidia GTX 980ti so I could get 4K resolution on the TV is use as a monitor. running mac OSX 10.12.1, used the latest mac osx drivers, cuda driver 8.0.53 and quadro driver 367.1510.15f03 and get great video on both the HDMI and Display ports, but no sound. in the alt/ audio the monitor is no longer listed as a sound output source, and in the mac system/hardware/audio section there are no options or devices listed as HDMI or Display Port. so it appears the mac os does not recognize the 980ti's display port, or HDMI outputs as audio output devices, but those ports do show up as graphics card outputs. in system/hardware/graphics displays. very maddening problem I cant seem to find a solution for so any help you can offer would be greatly appreciated. I dont want to distract you form the main issue of getting the sound up on this card in my mac pro, but there is a really crazy thing i just discovered. I put the ati card that is not rated for 4k output, back into the Mac so I could get sound until i find a soluiton for the 980ti and that ati card is putting out 4k to my display using the nvidia drivers!!!! Am i crazy?