Microsoft KB Archive/895962

= A USB 2.0 hub may stop working when you disconnect a USB 2.0 printer from your Windows XP-based computer =

Article ID: 895962

Article Last Modified on 3/25/2005

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional
 * Microsoft Windows XP Media Center Edition 2005
 * Microsoft Windows XP Tablet PC Edition 2005

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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
You disconnect a universal serial bus (USB) 2.0 printer from the USB port on your Microsoft Windows XP-based computer. In this scenario, an external USB 2.0 hub that is connected directly to another USB port on your computer may stop working.

Note This problem may also affect a port replicator that works as a USB 2.0 hub.



CAUSE
This problem may occur if either of the following conditions is true:  You are running Windows XP with Service Pack 1 (SP1), and you have installed the update that is described in the following article:

822603 Availability of the Windows XP Service Pack 1 USB 1.1 and 2.0 Update

 You are running Windows XP with Service Pack 2 (SP2) or a later version.



WORKAROUND
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 work around this problem, use one of the following methods.

Method 2: Disable power management of the USB 2.0 hub
Note This procedure may reduce the battery life on a portable computer.  Click Start, click Run, type devmgmt.msc, and then click OK. On the View menu, click Devices by connection. Expand the  node.

Note Because Microsoft Windows is installed on computers that use different types of processors, the  node may be named differently on your computer. For example, the  node might have any one of the following names:

ACPI Multiprocessor PC

ACPI Uniprocessor PC

Advanced Configuration and Power Interface (ACPI) PC

Standard PC

</li> Expand the PCI-Bus node.

Note If you do not see the PCI-Bus node, expand the current node, and then expand the PCI-Bus node.</li> Expand the  Enhanced Host Controller node.</li> Right-click the USB Root Hub node that is listed under the  Enhanced Host Controller node, and then click Properties.</li> Click the Power Management tab.</li> Click to clear the Allow the computer to turn off this device to save power check box, and then click OK.</li></ol>

Method 3: Edit the registry to disable selective suspend mode for all USB host controller drivers in the system
This procedure describes how to modify the following registry setting:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\USB

Entry: DisableSelectiveSuspend

Type: DWORD

Value: 1 disables selective suspend mode. 0 enables selective suspend mode.

Note
 * This procedure may reduce the battery life on a portable computer.
 * This setting affects all USB host controller drivers in the system. If the DisableSelectiveSuspend value is set to 1, selective suspend mode is turned off. Additionally, the Allow the computer to turn off this device to save power check box does not appear on the Power Management tab for the USB root hub.

<ol> Click Start, click Run, type regedit, and then click OK.</li> Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services

</li> On the Edit menu, point to New, and then click Key.</li> Type USB for the name of the subkey, and then press ENTER.</li> Click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\USB

</li> On the Edit menu, point to New, and then click DWORD Value.</li> Type DisableSelectiveSuspend for the name of the DWORD, and then press ENTER.</li> Right-click DisableSelectiveSuspend, and then click Modify.</li> In the Value data box, type 1, and then click OK.</li> Quit Registry Editor.</li></ol>

<div class="status_section">

STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.

<div class="moreinformation_section">

MORE INFORMATION
In Windows XP, the USB core stack supports selective suspend mode. A driver can use this mode to turn off the USB device that the driver controls when the device becomes idle. This mode works even when the computer remains in a fully operational power state (S0). For example, a driver can make the following devices idle:
 * The host controller.
 * The USB hubs, including the root hub.
 * The full range of USB devices that are supported by the operating system.

Selective suspend mode is primarily intended to conserve battery power in portable computers. Selective suspend mode helps reduce overall system power consumption by putting USB devices that are inactive in a low power state. This configuration increases battery life.

Keywords: kbtshoot KB895962

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