Just ordered a Moshi USB-C to DisplayPort cable from Amazon. As soon it arrives on Monday I can do some tests.
I hope it works out. There are a couple questions about USB support that are not clear in the manual. It seems there are three methods for USB support.
1) Thunderbolt USB controller. You showed this in your screenshot. The Thunderbolt USB controller of the display has two ports but only one seems to be used - it has a USB 3.0 hub connected internally where one port is used for the USB controls of the display (brightness control, etc.). Audio is only through DisplayPort or HDMI (LG UltraFine used USB audio). Devices can use USB 3.0 speed?
2) USB 2.0 USB-B input. The USB controller of your computer is used. Devices are limited to USB 2.0 speed.
3) USB-C input (via the Thunderbolt port for computers that don't have Thunderbolt). The USB controller of your computer is used. This supports USB 3.0 speed? If so then 5K2K 60Hz cannot be supported. So you will have to change the display option to get USB from the USB-B port. Hopefully the monitor is smart enough to allow 5K2K 60Hz over USB-C by not forcing USB 3.0 support. It would be better if the monitor supported switching the USB-C input between USB 2.0 and USB 3.0 speed so that only one cable would be required for USB and DisplayPort signals.
When two instead of one monitor are implemented for the LG 5K2K by OSX, SwitchResX can only export the EDID for the first monitor. For the second monitor there is not such option.
Very strange. It might be useful to create a program to read DDC directly, since it is unclear if SwitchResX is returning an unmodified EDID. There are some DDC programs for macOS to control options like brightness that could be easily modified to read both the EDID and DisplayID I2C addresses of DDC.
I think moninfo.exe (Monitor Asset Manager) in Windows uses DDC to read directly EDID.
Thus I can offer now 4 SwitchResX EDID Exports:
1.) LG 5K2K via DP1.4 port of GC-Titan Ridge:
LG HDR 5K Titan Ridge DP1.4(OK).txt. Correct 1x monitor implementation of the LG 5K2K @5120x2160 pix resolution without any custom resolution profile.
2.) LG 5K2K via TB3 port of the GC-TitanRidge without defining custom resolution profile:
LG HDR 5K Titan Ridge TB3 (2 Displays).txt.zip. Incorrect 2x monitor implementation of the LG 5K2K @ max 3680x2160 pix (Display 1) and max 2560x2160 pix (Display 2) resolution.
3.) LG 5K2K via TB3 port of the GC-TitanRidge with a custom resolution profile:
LG HDR TB 5K 2monitor .txt.zip. Incorrect 2x monitor implementation of the LG 5K2K @ 5120x2160 pix (Display 1) and 5120x2160 pix (Display 2) resolution. However only one screen with 5120x2160 is displayed on the LG 5K2K. Permanent switch between 1 und 2 Monitor implementation apparent in the SwitchResX GUI. During changes between 1x and 2x display OSX implementation of the LG 5K2K, black screen.
4.) LG 38UC99 via DP1.4 of the GC-Titan Ridge (3860x1600 pix) and LG 5K2K via TB3 port of the GC-TitanRidge with a custom resolution profile:
LG HDR 5K-TB3-OK.txt.zip. Correct 1x monitor implementation of the LG 5K2K @5120x2160 pix resolution in the SwitchResX GUI.
#3 and #4 are the same. Added custom resolutions does not create a custom EDID. Custom resolutions are stored separately from EDID in the Overrides files.
#1 has a mode for 5120 × 2160 @ 60.000Hz but #2 has only a mode for 2560 × 2160 @ 59.662Hz
#3/#4 are identical to #2 but have an extra Display ID extension block (version 1.1 where the rest are 1.2) containing the missing "5120 × 2160 @ 59.990Hz" resolution.
Maybe an error occurs in the case of #2 while reading the extra extension blocks from DDC. That doesn't make sense since #2 contains the proper extension block count at byte 7E of the first block.
I wonder if #3/#4 is the EDID to support DisplayPort 1.4 SST and #2 is the EDID to support DisplayPort 1.2 Dual Link SST.
I would like confirmation that this display can support 5K2K 60Hz from a Mac using Alpine Ridge (therefore using DisplayPort 1.2 Dual Link SST).
If the display is working as DisplayPort 1.4 700 MHz via Titan Ridge, then you should be able to disconnect one of the DisplayPort cables from the GC-TITAN RIDGE or connect it to a different graphics card.
I previously referred to the custom resolution apparent in my screenshot. In case of 3.) and 4.) above I also disabled postiv. sync in the custom resolution settings, which seems to display only one instead of two TB screens on the LG 5K2K with 5120x2160 TB screen resolution.
Interesting. We don't know exactly how Thunderbolt transforms DisplayPort signals.
What would be the DisplaVendorID of the LG5K2K to be found under /System/Library/Displays/Contents/Resources/Overrides?
Vendor = Manufacturer, so you need to look in the "DisplayVendorID-1e6d" folder. You can make a change in SwitchResX, save it, and view the files by Date Modified. There's an interesting file in there for the Thunderbolt port of this display (Product ID 7721; The DisplayPort has Product ID 7720). The DisplayProductID-7721.mtdd file describes the multi cable connection information for the display. The overlay data appears to be an EDID but it's different than the three you provided.