Is this monitor confirmed to be working at native 5k on z370 with an alpine ridge card? As in macos recognizes only the one display and not two that are split in half (only showing 1440p)? My macos installation refuses to boot with my z170 motherboard's thunderbolt enabled. It has the alpine ridge workaround but on boot it says it "couldn't allocate runtime area".
Maybe it has something to do with the fact I am booting off an nvme drive? When I enable thunderbolt it disables native pci-e, but one of my m.2 slots still works.
The weird thing is, when I took a screenshot in High Sierra with the same setup, the capture came out as 5120x2880, although I'm not sure if the monitor was outputting true 5k. When I take a screenshot in Mojave, it comes out as 2560x1440, which makes sense since it is being recognized as two monitors.
My best guess is without thunderbolt enabled the usb interface is disabled, but the alpine ridge card still funnels both displayport connections through thunderbolt 3, which causes macos to recognize 'two' monitors but there is only one. I'm thinking if macos can recognize the monitor over usb, the driver should load and it should work as intended, and not seen as two separate monitors. That theoretically would be solved by enabling thunderbolt on the motherboard.
I'm trying to figure out wether I should sell this monitor and replace it with one that is more compatible, or upgrade to z370 and get native thunderbolt 3 compatibility.
@joevt are you getting native 5k with your gigabyte board?