One of the most annoying Windows desktop-related issues I have run across over the past several years is related to Power Management. I routinely use sleep mode (with hibernate on my mobile computers), and rarely reboot my computers. In fact, on my primary computer (which sees a lot of virtualization and development-related action), I tend to reboot the computer weekly, or even less often. However, power management has not always worked as well as I would have liked. It seems that there are always applications and device drivers that want to interrupt what you do.
One such offender was Microsoft’s own Windows Media Center in Windows 7. While I didn’t know it at first, after deploying Windows 7 to my new workstation, my computer was automatically waking up each morning before I did (and I usually wake up pretty early). I tracked down the issue by running the “powercfg –lastwake” command. While it doesn’t always provide the most useful information, below is the result I received:
C: \Users\Anil>powercfg -lastwake
Wake History Count – 1
Wake History [O]
Wake Source Count – 1
Wake Source [O]
Type: Wake Timer
Owner: [PROCESS] \Device\HarddiskUolume2\Windows\System32\services .exe
Owner Supplied Reason: Windows will execute \Microsoft\Windows\Media Center
\mcupdatescheduled scheduled task that requested waking the computer.
Disabling “wake timers” in my power configuration profile didn’t seem to help. This pointed me to the “Scheduled Tasks” feature, where I was able to drill down to the source task. I unchecked the option to allow this task to automatically wake the computer, and all went well – no more automatic power-on signals at ~3:00am. Of course, the same approach could be used to troubleshoot other wake-related issues.
Knowledge of Power
While it’s not always easy to find, Windows OS’s contain a wealth of monitoring information and reports that can help track down various issues. One example is the built-in “System Diagnostics” report that can give you some insight into how your computer is managing power.
Unfortunately, I have still run into other power management-related issues, and nothing I have done has seemed to help. For example, on two different Windows 7 installations, I have had an issue where the monitors would automatically come out of power-saving mode. I regularly use three monitors, and want them to go into a low-power mode when I log off the computer. The monitors power off correctly, but they seem to wake at random times, even when no mouse, keyboard, or other devices are connected (or allowed to wake the computer). I’ve tested everything from potential Wake-on-LAN issues to installing and reinstalling software to no avail. I suspect that the issue might be a USB-to-DVI adapter that I have used on both computers, but I do need to use that (and unplugging it and uninstalling the drivers didn’t seem to help). If anyone has any suggestions, I’d be happy to try them!