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Possible cause for the U2711 sleep-wake looping issue identified

There had been mentioning of sleep-wake loop problems with Dell U2711 monitors. The sleep-wake loop is the constant sleep and waking up cycles of the monitor when the system attemps to enter monitor power save mode.

I discovered the problem may not lie in the monitor itself, but with Windows.

One cause of the sleep loop is caused by Windows display settings. With these new interfaces like Displayport and HDMI, the more-trouble-than-they-are-worth feature of syncing causes problem with the display configuration in Windows. When DP/HDMI loses sync due to sleep states, Windows will attempt to switch to another display configuration profile. If the profiles are not identical, a sleep-wake loop will ensue.

By identical profiles, I am referring to in case of different number of display being connected or turn on in a multiple display system; resolutions, orientations of the still-turned-on displays need to be set identically throughout. One can do so by changing the display settings at every possible combination of your monitors being on/off and ensuring they share the same resolution, orientation across the combinations.

I hope this helps someone.

I hope Dell liaison with Microsoft to get a software fix as well.

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Re: Possible cause for the U2711 sleep-wake looping issue identified

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Re: Possible cause for the U2711 sleep-wake looping issue identified

I've been having the same problem.  I'm using a displayport to HDMI adapter cable, purchased from Dell, to connect to an HP 27" monitor.  When the laptop goes to sleep, the external monitor does as well, but you hear the continuous windows sound of a device connecting/disconnecting.  

The two monitors had not been set to the same resolution... the external is 1920x1080 and the laptop is 1920x1200.  After seeing this post, I changed the laptop to 1920x1080, but it did not fix the problem.

I'd love to solve this problem, as the sound is driving my wife and I nuts, and it can't be good for the system to be turning on and off all night.   The above post is the only mention of this problem that I have found anywhere on the internet.  

I'm considering buying a displayport to DVI cable and using that instead.  I don't need the audio.  I'll let you know if that takes care of the problem.

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