10-25-2018 11:48 PM - edited 10-25-2018 11:50 PM
This is what I got when I am using the HDMI port as output to my 4K monitor.
There is no issue with the monitor I am using (LG 27UD68) and the cable I am using (High-Speed HDMI Amazon Basic).
The monitor works perfectly (4K@60Hz) on other HDMI devices, such as my PS4 PRO, NVIDIA SHIELD, XBOX ONE X.
And it also works perfectly (4K@60Hz), when I am using the USB-C port through a USB-C to DisplayPort cable to output video to this monitor.
I cannot find why 4K@60 is not an option on this device through HDMI,
If the port is HDMI 1.4 then it should possibly be limited at 4K@30.
This might be a driver issue with the Vega 8 graphics adapter, but I cannot tell.
And Lenovo technician should work on this issue.
11-29-2018 11:21 AM
I got 4K60Hz working on my Sharp 4K Roku TV through HDMI,
I went to advanced display properties and changed the refresh rate to 60.
I also confirmed that the TV runs at 60Hz by checking status and
testing it using the UFO test.
Why I can only get 4K@50Hz on that LG monitor still unknown and need further testing.
11-29-2018 07:26 PM - edited 11-29-2018 07:26 PM
I don't have a solution either, but AMD's Ryzen APUs supports HDMI 2.0 spec.
A quote from another forum that may be tangentially related?
"The fix is to go in the Monitor menu and make sure "Ratio" under "Quick Settings" is 1:1 or Original (NOT Wide). For me it was set to Wide when I got it, and when in "Wide" it limits to 30Hz."