I recently bought a PG279Q, and intended to use it with the dual inputs for both of my computers while I'm waiting on the movers to transport my other monitors halfway across the country. I first connected it to my gaming PC (Windows PC with a GTX 1080) via DisplayPort, and everything was great. However, when I tried to connect it to my workstation (a Hackintosh, with a GTX 750 Ti) via HDMI, I found that it was apparently being detected as a TV (see screenshot), and limited to only 1080p resolution with underscan settings.

At first I wasn't sure if it was an issue with the GPU, so I did some testing, and found that it appears to be an issue with either OS X or the monitor specifically, based on these results:

Hackintosh (OS X) - GTX 750 Ti, HDMI: Not working - limited to 1080p
Hackintosh (OS X) - GTX 750 Ti, DP: Working - runs at 2560x1440/165Hz
2012 MacBook Pro Retina 15" (OS X) - Intel HD4000 iGPU / GT 650M dGPU: Not working - limited to 1080p
2013 MacBook Pro Retina 13" (OS X) - Intel HD4000 iGPU only: Not working - limited to 1080p
Gaming PC (W10) - GTX 1080, HDMI: Working - runs at 2560x1440/60Hz
Gaming PC (W10) - GTX 1080, DP: Working - runs at 2560x1440/165Hz

Ideally I would test the Hackintosh hardware running Windows, as well as the rMBPs using miniDP (via TB port) to DP input, but I don't have the extra HDD / cables to do so at the moment, and even with the current results it's fairly safe to say there's no issues with DP.

So, I know being a high-end gaming monitor means that the number of people who have connected it to Macs via HDMI is probably low, but has anyone else (especially anyone from ASUS) run into this? I'm curious as to whether this is a problem with OS X or the monitor, and if it's the monitor, if it's the G-Sync module (not sure whether it's involved in the data chain when using HDMI, since G-Sync is not enabled on that input, but I've spoken to someone who ran into the same issue on an Acer XB271HU which is another G-Sync monitor).