I haven’t been able to track what has changed. The display will resync after change from Limited to Full and vice versa with nvidia-settings, but the output is always in Limited mode. This was working properly (set to Full) for about 6 months. Powercycling all equipment was ineffective. Forcing the setting in xorg.conf is also ineffective. What else can I check?
Ubuntu 16.04
nvidia-387 and nvidia-390
4.4.0-112-generic and 4.4.0-116-generic and
GT 1030
HDMI-0 connected 3840x2160+0+0 (0x1c9) normal (normal left inverted right x axis y axis) 1600mm x 900mm
Identifier: 0x1bd
Timestamp: 40311
Subpixel: unknown
Gamma: 1.0:1.0:1.0
Brightness: 1.0
Clones:
CRTC: 0
CRTCs: 0 1
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0
EDID:
00ffffffffffff0011ee4e0001010101
001a010380a05a780aee91a3544c9926
0f5054a1080031404540614071408180
01010101010108e80030f2705a80b058
8a0040846300001e023a801871382d40
582c450040846300001e000000fc0044
454e4f4e2d41565248440a20000000fd
003a791e883c000a20202020202001ab
020372f15f6160101f66650413051403
021220212215015d5e5f6263643f400e
230f241e380f7f073d1ec01507505f7e
03570601677e014d02005f7e01835f00
006e030c002200b83c20008001020304
67d85dc401788003e20f33e3060d01eb
0146d000260a0975805b6ce305c000e2
00cf00000000000000000000000000ef
BorderDimensions: 4
supported: 4
Border: 0 0 0 0
range: (0, 65535)
SignalFormat: TMDS
supported: TMDS
ConnectorType: HDMI
ConnectorNumber: 1
_ConnectorLocation: 1