You have encountered the Timeout Detection and Recovery (TDR) feature. Originally developed for Windows Vista SP1, Microsoft created TDR because video card drivers are one of the main causes of instability in a Windows systems. The new feature -- which is also in Windows 7 -- fixes graphics card freezes without requiring a user to reboot his or her system.
Crash into me: How Timeout Detection and Recovery works
The video scheduler -- a component of the Windows graphics stack -- parcels out a certain slice (or "quantum") of system time to the video subsystem. If the graphics processing unit (GPU) takes more than the allotted amount of time to complete its actions, the video scheduler begins to count the time elapsed with no response. The default timeout period is two seconds, and if the GPU doesn't respond in that two-second window, the video scheduler informs the operating system (OS) that the graphics card is probably hung or frozen.
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As a result, the OS kills the video driver, resets the video hardware and restarts the entire graphics stack. Also, it restores as much of the existing state of the desktop as possible. Some applications may die completely during this time if they aren't crash-aware, but the whole system remains up. In the end, the user receives a warning on his or her desktop about the entire incident.
If six or more of these errors occur within one minute, the OS decides the system is too unstable to keep running and it will halt with a bug check -- also known as a Blue Screen of Death (BSOD).
You can change the crash timeout values used by the system by editing the registry entries, which alters the number of driver timeouts tolerated by the system before it BSODs. However, the mere presence of these problems is a sign something else needs to be fixed.
Fixing video driver errors
Most of the time, video driver errors occur because the video driver itself is not up to snuff. I have often encountered these incidents while using a beta version of a driver, and upgrading to the release version usually solved the problem. Note that sometimes it's necessary to fall back to an earlier release version if the current release is causing the problem.
If you have changed video driver versions and the errors continue, then there are a couple of other possibilities to explore.
First, check to see if the power supply in the PC is doing the job, especially for video cards supporting multiple displays, which use much more electricity. If the system's power supply can't consistently deliver what the card needs, then the output from the power supply may dip and cause a system failure. Any video card that requires its own separate power connector should be considered that much more of a drain on the power supply.
Furthermore, the card itself may be defective. Determining if this is the case can be difficult because simply switching the current card for another one doesn't necessarily work. For instance, if you swap it with a card that doesn't use an external power connector, you could be missing out on the power supply being a contributory factor. A failing motherboard could also be the culprit, but this option should only be considered if everything else has been explored and exhausted.
ABOUT THE AUTHOR
Serdar Yegulalp is editor of the "Windows Power Users Newsletter." Check it out for the latest advice and musings on the world of Windows network administrators.
This was first published in June 2010
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