Microsoft KB Archive/303777

= After You Install a Visioneer USB Scanner the CPU Usage May Be Unusually High =

Article ID: 303777

Article Last Modified on 1/15/2006

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional

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This article was previously published under Q303777



IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SYMPTOMS
When you use a Visioneer universal serial bus (USB) scanner, your computer may experience a sudden, unusually high amount of CPU usage. After the scanner is installed, Task Manager may report that the service host program (Svchost.exe) utilizes 10 to 30 percent of the CPU. However, when you disable the scanner by using Device Manager, the unusually high amount of CPU utilization is stopped (and lowered).



CAUSE
This problem can occur because the device drivers that are used with these scanners &quot;poll&quot; a device to receive device notifications, such as, button pushes. USB provides a separate pipe that the device driver can use to support device events, but the firmware of the scanner does not use this feature, and therefore causes the devices to be polled.



RESOLUTION
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To resolve this problem, either disable polling for the scanner or increase its poll timeout value:  Locate the scanner in the following registry:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Class\{6BDD1FC6-810F-11D0-BEC7-08002BE2092F}

NOTE: Under the preceding registry key, you may locate multiple subkeys, the actual number of which depends upon how many imaging devices that you have installed. The scanner can be identified by the device name in one of the strings. You may have more than one subkey for your scanner if you plugged the device into different USB ports and the manufacturer did not use serial numbers for the device. In this situation, you can often observe a &quot;#2&quot; after the device name that corresponds to the correct version as listed in Control Panel.

 When you have located the device key for your scanner, open the following DeviceData subkey:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Class\{6BDD1FC6-810F-11D0-BEC7-08002BE2092F}\0000\DeviceData

NOTE: There can be multiple values in this key, such as, Server and TwainDS.

 To change the polling time interval, create a new DWORD value under DeviceDate called PollTimeout, and then set its value to have a polling interval in milliseconds. A value of 1000 can poll every second. The default value is set at 700. To disable the button functionality and the polling capability, create a new DWORD value called DisableNotifications, and then set the value to 1.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

Keywords: kbenv kbprb KB303777

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