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I have three monitors connected to my computer. Two using my GTX 550 and the last is connected to my mainboard.

On Windows, all three monitors work like expected, but I get problems when running Ubuntu 15.04 (also tested in previous versions).

I read very much about it, but my problem seems to be a bit special, because the third monitor is even recognized, but not working properly.

For you to understand my problems, I recorded my screens and uploaded a video of it:

http://ercksen.de/triplemonitor_issue.mp4

The right screen is the one connected to the onboard intel graphics.

I used Ubuntu Unity there, but also the Gnome flashback did not work.

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I have 3 monitors, two DELL and one smaller HP L1750 and two video cards running OK:

01:00.0 VGA compatible controller: NVIDIA Corporation GF108GL [Quadro 600] (rev a1) 00:02.0 VGA compatible controller: Intel Corporation Xeon E3-1200 Processor Family Integrated Graphics Controller (rev 09)

My three monitors:

xrandr --query

Screen 0: minimum 8 x 8, current 3200 x 1200, maximum 16384 x 16384

DVI-I-0 connected primary 1600x1200+1280+0 (normal left inverted right x axis y axis) 367mm x 275mm
   1600x1200      60.0*+
   1280x1024      75.0     60.0  
   1152x864       75.0  
   1024x768       75.0     60.0  
   800x600        75.0     60.3  
   640x480        75.0     59.9  

DP-0 connected 1600x1200+1600+0 (normal left inverted right x axis y axis) 367mm x 275mm
   1600x1200      60.0*+
   1280x1024      75.0     60.0  
   1152x864       75.0  
   1024x768       75.0     60.0  
   800x600        75.0     60.3  
   640x480        75.0     59.9  

DP-1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)

VGA1 connected 1280x1024+0+176 (normal left inverted right x axis y axis) 340mm x 270mm
   1280x1024      60.0 +   75.0* 
   1152x864       75.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3  
   640x480        75.0     72.8     60.0  
   720x400        70.1  

VIRTUAL1 disconnected (normal left inverted right x axis y axis)

  1280x1024 (0x327)  108.0MHz
        h: width  1280 start 1328 end 1440 total 1688 skew    0 clock   64.0KHz
        v: height 1024 start 1025 end 1028 total 1066           clock   60.0Hz
  1280x1024 (0x326)  135.0MHz
        h: width  1280 start 1296 end 1440 total 1688 skew    0 clock   80.0KHz
        v: height 1024 start 1025 end 1028 total 1066           clock   75.0Hz
  1152x864 (0x328)  108.0MHz
        h: width  1152 start 1216 end 1344 total 1600 skew    0 clock   67.5KHz
        v: height  864 start  865 end  868 total  900           clock   75.0Hz
  1024x768 (0x32a)   65.0MHz
        h: width  1024 start 1048 end 1184 total 1344 skew    0 clock   48.4KHz
        v: height  768 start  771 end  777 total  806           clock   60.0Hz
  800x600 (0x32b)   49.5MHz
        h: width   800 start  816 end  896 total 1056 skew    0 clock   46.9KHz
        v: height  600 start  601 end  604 total  625           clock   75.0Hz
  800x600 (0x32c)   40.0MHz
        h: width   800 start  840 end  968 total 1056 skew    0 clock   37.9KHz
        v: height  600 start  601 end  605 total  628           clock   60.3Hz
  640x480 (0x32d)   31.5MHz
        h: width   640 start  656 end  720 total  840 skew    0 clock   37.5KHz
        v: height  480 start  481 end  484 total  500           clock   75.0Hz

From the first moment three monitords had been working ok, but with a little problem: Always i must to reconfigure the monitors configuration at starting ubuntu... everyday!

But is the first ubuntu in witch the 3 monitors configuration has runed without modifying configuration files. All has been done with the default Ubuntu monitor configuration tool.

Ah, this is that I had to do in Ubuntu 14.10 to have 3 monitors running (I had problems Ubuntu to detect my third monitor:

sudo xrandr --newmode "1280x1024_60.00" 135.00  1280 1296 1440 1688  1024 1025 1028 1066 +Hsync +Vsync
sudo xrandr --addmode VGA1 1280x1024_60.00
sudo xrandr --output VGA1 --mode 1280x1024_60.00
  • That does not work for me to add a new mode, I have no problems with detecting monitors. Seems that I have to switch to SLI or use a graphics card that supports three monitors. – Ercksen May 24 '15 at 11:03
  • This is working only when you save xorg.conf to your X11 conf dir, For Ubuntu 16.04 this is /etc/X11/xorg.conf – podarok May 13 '17 at 15:19

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