0

Problem Formulation: Dual-Monitor setup currently not possible because monitor not detected when plugged in any DP.

Symptoms:

  • If monitor A is connected to HDMI and monitor B to any DP slot, only monitor A has a picture after boot. Any monitor connected to a DP slot never shows up in Display-Settings.
  • If monitor A or B is connected to a DP slot while the HDMI slot is kept free, that monitor works normally, but the monitor still doesn't show up in Display-Settings.
  • When monitor A is connected to HDMI and B to a DP slot, while booting, both monitors show grub at the same time. So here it seems to work. As soon as it is booted, picture is only shown on the monitor that is plugged into HDMI slot. So problem with cables, adapter and gpu can be ruled out?
  • Under Win7 same Problem persists

Setup:

  • Radeon rx480 with 1x HDMI and 3x DP
  • Ubuntu 16.04
  • two Acer monitors with a max. res. 1920x1080 and 60hz
  • Adapter: female HDMI, male DP

xrandr output with monitor A connected to HDMI and monitor B connected to DP-2:

Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
DisplayPort-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-1 disconnected (normal left inverted right x axis y axis)
DisplayPort-2 disconnected (normal left inverted right x axis y axis)
HDMI-A-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 527mm x 296mm
   1920x1080     60.00*+  50.00    59.94  
   1680x1050     59.88  
   1280x1024     60.02  
   1440x900      59.90  
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      70.07    60.00  
   800x600       60.32    56.25  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       66.67    60.00    59.95    59.94  
   720x400       70.08  

xrandr output with monitor A conencted to DP-2 slot and HDMI slot kept free:

Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
DisplayPort-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-1 disconnected (normal left inverted right x axis y axis)
DisplayPort-2 disconnected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
HDMI-A-0 disconnected (normal left inverted right x axis y axis)
  1920x1080 (0x5a) 148.500MHz +HSync +VSync
        h: width  1920 start 2008 end 2052 total 2200 skew    0 clock  67.50KHz
        v: height 1080 start 1084 end 1089 total 1125           clock  60.00Hz

EDIT: lspci -nnk | grep -i VGA -A2 gives:

01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 470/480/570/570X/580/580X] [1002:67df] (rev c7)
    Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] Radeon RX 480 [1002:0b37]
    Kernel driver in use: amdgpu
  • Manufacturer: AMD
  • Name: Ellesmere [Radeon RX 480]

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.