I have recently put in a 390x into my mackintosh but I seem to be having some issues with the card. Here is the build: OSX Sierra 10.12 Intel 6700k Gigabyte Z170MX Gaming 5 HP AMD R9 390X Aries-E3 8GB Video Card Gigabyte AMD HD 7870 The problem I am facing is making the card work properly. I am right now making the card work by booting with the 7870 pluged in and then switching the DVI cable to the 390x DVI port one and then the second DVI port on the card. I don't know why i need to switch a second time, but graphics acceleration will not happen if I don't. I followed everything from this guy https://techbangtheory.com/2016/06/26/skylake-hackintosh-with-dual-amd-r9-390x/ If anyone could give me some advice, I don't want to have 2 giant GPUs in my pc and only use one. I have tried this setup with a Nvida 730 but I found a hit on graphical performance so somehow it is using both GPUs.