That's been done with the old LG UltraFine 5K many times by many people. What bluepr0 says is something new:
The new LG UltraFine 5K is different than the old LG UltraFine 5K because the new one has a Titan Ridge Thunderbolt controller instead of an Alpine Ridge Thunderbolt controller.
The Titan Ridge Thunderbolt controller lets you connect the display to a computer that doesn't have Thunderbolt but only at 4K resolution because that mode uses a single DisplayPort signal from USB-C DisplayPort alt mode (this display doesn't take 5K 60 Hz from DisplayPort 1.4).
When connected to a Thunderbolt computer, the display can take two DisplayPort 1.2 signals to make 5K 60Hz 10bpc. I think what bluepr0 is saying is that the display will also accept a single DisplayPort signal over Thunderbolt. I think that is possible because that is what it does when connected via USB-C DisplayPort alt mode. I don't remember if the old LG UltraFine 5K allowed a single DisplayPort signal over Thunderbolt. In dual DisplayPort mode, my Dell UP2715K will accept a single DisplayPort signal from the first port to get 4K.
But the test with the Moshi cable saw no 5K resolution. A DisplayPort signal through Thunderbolt probably won't change that. Also, DisplayPort 1.4 only has 75% the bandwidth of Dual DisplayPort 1.2, so 5K 60 Hz can only have 8 bpc instead of 10 bpc.
From that one Moshi test I've seen, the new UltraFine 5K does not have the Thunderbolt + USB-C + DisplayPort 1.4 capabilities that the LG 34WK95U-W (5K2K) display has.
I would like to see output from the following command:
Code:
/System/Library/Extensions/AppleGraphicsControl.kext/Contents/MacOS/AGDCDiagnose -a > AGDCDiagnose_a.txt
It should show DisplayPort version, max link speed (HBR2 for DisplayPort 1.2 and HBR3 for DisplayPort1.4), max link width (4 lanes usually), and current link speed and link width. It should also show EDID. For Thunderbolt, it should show info for both DisplayPort signals (EDID for each half of the screen will be different). I think this info might be available only for Intel or AMD graphics.