On a Windows 7 computer, upon startup, the user might observe the following behavior:
1. Turn on the computer and Windows starts.
2. After “Starting Windows” message is dispalyed, the screen turns black for a few seconds.
3. The user might also see some text stating that no video input is detected and that the monitor is entering power saving mode.
The above is expected behavior.
When “Starting Windows” is displayed, Windows OS kernel is performing Windows OS initialization. Windows kernel is responsible for providing monitor display in basic video mode.
After OS initialization completes, display mode is switched to a more advanced video mode. This video mode switch is normal behavior on a Windows 7 system. The video mode switch happens after “Starting Windows” and before LogonUI is ready.
During the video switch, Windows initializes the new video mode. The initialization involves device re-enumeration. And it completes after device re-enumeration is done.
During the video initialization, there is no input to the display monitor device. We might see a few seconds of black screen and monitor entering power saving mode if device re-enumeration take a few seconds because video initialization does not complete before the display monitor detects no input.
The time on device re-enumeration will be different for different hardware models. It could be affected by:
1. Number of PNP devices
2. Time on query/status check on each device
For different hardware models, it is expected behavior to have a different video initialization time consumption. If the process takes a few seconds, we might see monitor turning into black and entering power saving mode. (When\Whether the monitor will enter power saving mode depends on the monitor hardware.)