Issues getting 4k 60hz from mac / 980ti to TCL 65S405 4k tv
I needed a 65" 4k tv for other reasons, but I do some video editing, so looking to get most accurate image for editing.
Just updated the old 2008 MacPro with a mac flashed 980ti, and picked up a TCL 65S405 4k tv. Mac is running most updated possible OS for it which is 10.11.6.
Since it's on a mac, though, I don't have Nvidia control panel, and system options gives only 30hz or 24hz output options, and image is way too small (underscanned?) The card has 3 DisplayPorts, and 1 HDMI 2.0 port, and Tv's docs say all of it's 3 HDMI inputs are 2.0 as well, so I'm not seeing anything incapable of 60hz. Fairly sturdy thick looking 6 foot HDMI cable, though I can't speak for it's particular rating.
Image is set at correct UHD resolution, but shrunk and severely letterboxed several inches or more on all sides. Do I need SwitchResX to force overscan and dial in, or is there some way to just get correct pixel mapping without shrinking and then enlarging it?