A Mind Lost

Anything and everything.

Windows 7 Display Power Management Problems

A problem I’ve had with Windows 7 since its release has been it’s inability to properly resume after turning off the display(s).  Apparently this behaviour is caused by a mysterious conflict involving display power management, a hidden taskbar, and no active application windows displayed.  When the system attempts to turn the display back on, Windows becomes unresponsive.  Sometimes the display remains black, although the backlight is turned on, and other times the desktop/login screen will display, but do not respond to any input.  Leaving the system for an indeterminate (and apparently random) length of time will, on occasion, allow Windows to sort itself out and return control.  Most folks just hit the power button and restart their system.

I’ve been trying to find a fix for this for well over a year, having been resigned to manually turning off my monitors whenever I know I’m going to be away for any length of time. After looking around to see if anyone had found a solution since the last time I checked, I found the thread linked to above.  One user, LowQCab listed the various BIOS settings he tried while searching for a resolution.

So….  Here is the exact setting that solved my problems :

In my BIOS , under “Power” there are several different settings that control
how the BIOS will communicate with the OS,
Here are my options ,  ( yours may vary from mine of course ) ,

Under  “POWER”…………

I tried disabling :  ACPI 2.0 Support , result = boot to black monitors , no OS .

I tried disabling :  ACPI  APIC Support , same result , boot to black monitors , no OS .

Then I tried changing :  SUSPEND MODE ,  the default is  “AUTO” ,
the options are :
S1 (POS) only
S3  only
AUTO

After I changed this setting to  “S3 only” …..  No more problems  😀  .

Of course, turning off ACPI/APIC will render Windows unbootable and requires a reinstall if one wishes to leave these settings disabled.  But the interesting part of his post is the mention of the ACPI Suspend Mode.  My system was set to Auto, which allows the OS to select which mode to use, while LowQCab suggests changing this to S3 only.

I’ve effected this change in my own BIOS and gave it a test by setting Windows to power down the displays after 1 minute, and it appears to have worked.  Time will tell if this is a lasting solution or not.

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