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DisplayPort Blanking / Screen Autodetect Problems

posted Jun 20, 2013, 7:30 PM by Robert Jones   [ updated Jun 20, 2013, 8:18 PM ]
DisplayPort (DP) is nice new digital display interface with a host of benefits over previous interfaces.  Unfortunately it comes with a major headache when used with Windows and multiple screens.  Whenever you do anything on the port that triggers a disconnect Windows decides that it must shuffle everything around because you may have connected a new display or may have windows hidden on some missing display.  This feature, which cannot be disabled, is intended to be helpful but it turns out very annoying because you are continually having to re-setup your desktop.  

This feature is triggered by things like: 
  • screen mode switches; 
  • screen power; 
  • cable changes (ok that seems almost fair); 
  • any fluctuation on the hot-plug pin 18.
I use 4 displays in a 2x2 cube arrangement which are never turned off, but occasionally (1-3 days), Windows screen detection is triggered causing windows to move to one screen and the screen layout is changed.  The only way to reliably recover is by rebooting.  I have never determined what causes the trigger so had to find a way prevent or ignore it.

I tried many sources for help and information but always came up a bit short.  There have been various frustrations over this with some resorting to butchering wires or trying screen management software or resorting to alternative interfaces.  Butchery is unacceptable to me; software did not resolve it; alternative interfaces was regrettably going to be the way forward but that presented it own challenges trying to identify what new cards/converters were needed.

I found a way to hard-set the screen connection setup which prevents Windows from trying to do anything with connection changes.  This applies to NVIDIA cards in my case but may apply elsewhere.  Here were my steps:

  1. NVIDIA control panel (right-click on the desktop). 
  2. go to system topology 
  3. find your screens in the tree and the link for EDID information that currently says [Read from] monitor - click it to change it. 
  4. Export the monitors current EDID information to a file, then load it back in so that the EDID information is alway read from the file.
  5. Repeat this step for each monitor making sure to use a different and identifiable filename for each one.
  6. The topology will then list each display as either EDID 'forced' or 'file'.
I can now switch off screens, disconnect and reconnect them and Windows does not change anything about the way they are configured anymore.

NVIDIA will warn you that you cause damage to your screens if the EDID information is wrong for your monitor.  This might be true so just remember to Unload the EDID before making any screen connection/hardware changes just in case.

Other pages with similarly frustrated people:
I hope this helps others -- Please let me know if this does/does-not work for you.