intel graphics - Change monitor refresh rate for 4k monitor - Ask Ubuntu

i try change external monitor refresh rate iiyama prolite x4071uhsu-b1 monitor on xng p406 laptop. i'm using internal intel gpu.

xrandr gives me:

edp1 connected primary 1920x1080+0+961 (normal left inverted right x axis y axis) 309mm x 174mm    1920x1080     60.02*+  59.93      1680x1050     59.95    59.88      1600x1024     60.17      1400x1050     59.98      1600x900      60.00      (...)  dp1 connected 3840x2160+1920+0 (normal left inverted right x axis y axis) 878mm x 485mm    3840x2160     60.00 +  30.00*   29.97      1920x2160     60.00      2560x1440     59.95      2048x1152     60.00     (...)  

so, 60hz should available, not used.

so try switch 60 hz xrandr --output dp1 --rate 60. nothing happens. no output in console, no flickering or something. , xrandr gives same output above.

am doing wrong?

my ubuntu: 16.04 4.7.2-040702-generic kernel

jiipeezz pointed me right direction: edited file ~/.config/monitors.xml command sudo gedit ~/.config/monitors.xml , changed <rate>30</rate> <rate>60</rate> , rebooted. works, xrandr output is:

dp1 connected 3840x2160+1920+0 (normal left inverted right x axis y axis) 878mm x 485mm    3840x2160     60.00*+  30.00    29.97      1920x2160     60.00      2560x1440     59.95