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I have a dual screen setup here, with an AMD video card.

The display connected to the DVI cable blinks (i.e. turns off and on) all the time, while nothing happens to the display connected to the VGA. When I swap the cables, the problem occurs on the newly connected display.

What could be happening? Could the CPU's power supply not be powerful enough?

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When you say you swap the cable, does this mean the cable is at fault or, it's only the DVI connected monitor which blinks regardless of cable? Not sure what this has to do with arch-linux so I removed the tag. – Dave Aug 12 '13 at 12:40
The CPU's energy source?! – David Schwartz Aug 12 '13 at 20:13
Did the dual setup ever work? Also, the CPU doesn't have a power supply per se. The power supply comes from the PSU as David suggests... Did you mean the PSU or the distribution? What PSU wattage do you have? – Dave Aug 13 '13 at 7:45

This is very hard to answer as your question is broad, but it could be power, it could be a faulting port, it could be a faulting graphic card.

Try a different DVI cable.
Try only plugging in DVI (not VGA) so only 1 cable is in. Try a different monitor
Try borrowing another GPU
Try putting your GPU into another machine

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I've had the same problem connecting my laptop to a monitor, getting flickering screens, but I think I might have found a solution.

  1. Go to (I am running Windows 7): Control Panel\All Control Panel Items\Power Options\System Settings
  2. Edit the "When I close the lid" to "Do nothing" on both options.
  3. Close the lid of the laptop.

You will now see that the screen is no longer blinking. Try opening the laptop lid again, and they all work fine.

It might seem a bit far fetched, but give it a try, it worked for me:)

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Try turning down the resolution. A little lower each time until it stops blinking. If you get to like 800x600 or something....and it hasn't stopped then that's not it.

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Try with a short (less than 3.5 meters) cable. If it works, then it's the cable causing signal loss. For HDMI there are good quality silver-plated cables which provide good signal integrity. You can utilize such cable with DVI->HDMI->DVI connectors.

Pls note - in AMD/ATI videocards you can't mix DVI/HDMI/Display port simultaneously. It won't cause monitor blinking but monitor to be disabled.

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What do you mean you can't mix DVI/HDMI and Display ports? This reads as if you can only have 1 cable to 1 monitor if you can't utilise all 3? – Dave Aug 13 '13 at 7:32

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