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ubuntu-12.04xrandr

setting 4k resolution with xrandr fails with badmatch error

I have a 4k monitor and try to set my Ubuntu 14.04 LTS to use it. Since there is no 3840x2160 option available in system settings and NVIDIA X Server Settings - the only way to do that is using xrandr tool. So I type: 

gtf 3840 2160 60

# 3840x2160 @ 60.00 Hz (GTF) hsync: 134.10 kHz; pclk: 712.34 MHz
  Modeline "3840x2160_60.00"  712.34  3840 4152 4576 5312  2160 2161 2164 2235  -HSync +Vsync

xrandr --newmode test87 712.34  3840 4152 4576 5312  2160 2161 2164 2235  -HSync +Vsync

xrandr --addmode HDMI-0 test87

X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  18 (RRAddOutputMode)
  Serial number of failed request:  35
  Current serial number in output stream:  36

It seems like a common error, but other solution suggest modifying the /etc/X11/xorg.conf (that I don't have, I tried to create one and reboot but it does not help). Some others solutiond suggest using brackets around mode names - it does not help as well.

Solution

  • If I'm not entirely mistaken 4k@60Hz is simply beyond the bandwidth capabilities of HDMI-1.4; you either need to connect via DisplayPort or use a lower refresh rate; 30Hz would be a safe bet.

    Update

    Given the EDID data dump everything looks fine so far. The xorg.conf entries that correspond to your display would be these (generated by parse-edid, which would be equivalent to what the X.org server does).

        # EDID version 1 revision 3
Section "Monitor"
    # Block type: 2:0 3:fd
    # Block type: 2:0 3:fc
    Identifier "ASUS PB287Q"
    VendorName "ACI"
    ModelName "ASUS PB287Q"
    # Block type: 2:0 3:fd
    HorizSync 24-160
    VertRefresh 30-80
    # Max dot clock (video bandwidth) 300 MHz
    # Block type: 2:0 3:fc
    # DPMS capabilities: Active off:yes  Suspend:no  Standby:no

    Mode    "3840x2160" # vfreq 30.000Hz, hfreq 67.500kHz
        DotClock    297.000000
        HTimings    3840 4016 4104 4400
        VTimings    2160 2168 2178 2250
        Flags   "-HSync" "+VSync"
    EndMode
    Mode    "1920x1080" # vfreq 60.000Hz, hfreq 67.500kHz
        DotClock    148.500000
        HTimings    1920 2008 2052 2200
        VTimings    1080 1084 1089 1125
        Flags   "+HSync" "+VSync"
    EndMode
    # Block type: 2:0 3:fd
    # Block type: 2:0 3:fc
EndSection

    Note the UHD resolution mode.

    Hadn't you mentioned that the NVidia X Server Settings tool can be used I'd have suspected a broken driver installation. Anyway I strongly you double check, that the drivers are properly installed and nothing is interfering with them.