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I am running Ubuntu 14.04.3 64-bit, and have two Dell 17" monitors connected at a single VGA port. Both monitors are on, and mirror the same display. I am not able to detect the second monitor, when running "Detect Displays". Here's the output of xrandr -q

Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 8192 x 8192
DVI-I-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
VGA-1 connected primary 1280x1024+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1280x1024      60.0*+   75.0  
   1152x864       75.0  
   1024x768       75.1     60.0  
   800x600        75.0     60.3     56.2  
   848x480        60.0  
   640x480        75.0     60.0     59.9  
   720x400        70.1  

I tried disconnecting one monitor. This changes the detected display from "Unknown" to "Dell 17". I also tried connecting the second monitor at the DVI port, but that alters my primary monitor display, I lose the mouse, and have no way to operate properly. What hardware setup is ideal for dual monitors? How do I solve this problem? I appreciate your feedback.

Thanks, Anjy

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Two monitors on a single VGA port? That's kind of like putting two lightbulbs in a single socket and expecting them to blink on and off separately.

Outside of certain DisplayPort configurations, each monitor has to be on a separate physical port, especially of that port is an analog connection like VGA.

One monitor on VGA and one on DVI should work, depending on your video card, one one on DVI and one on HDMI.

Changing the configuration and losing the mouse sounds more like a display configuration issue unrelated to hardware. You may need to go in to your display configuration panel and change things.

| improve this answer | |
  • Dear Stephen, I have used a VGA splitter cable to attach two monitors to the same port for a decade now, and it always worked for me in the past. I did try adding the second monitor to a DVI port, but my mouse disappears, along with any open terminals or other applications. So once I connect the second monitor at the DVI port, I no longer have the ability to configure the display. – Anjy Jul 13 '16 at 3:12
  • It turned out that my problem was a hardware problem. I found a third monitor that was newer, and plugged it into the DVI port, and everything worked like a charm. Thanks again everyone! – Anjy Jul 13 '16 at 5:56

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