Problems may occur when you try to transfer files to or from a device that is connected to a USB 2.0 hub

Resolution for Windows 7

To resolve this problem in Windows 7, add a EnHcSoftRetry registry entry with a DWORD value of 1 under the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\PCI\<hw id>\<instance id>\Device Parameters

Note To obtain <hw id> and <instance id>, open the Device Manager property page for each EHCI USB host controller, click the Details tab, and then select Device Instance Path in the list. Most systems have only one or two EHCI host controllers, so this should not be too difficult.

Hotfix information for Windows Vista

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Hotfix information for Windows XP

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Behavior after the hotfix is applied

When this hotfix is applied and the Soft-Retry functionality is enabled with the appropriate registry value (depending on the Windows version, as described above), a USB transfer that fails for specific reasons is silently retried instead of completed and given a "failure" status. When this process occurs, USB client device drivers may not receive notification that communication with the device failed because of a lower-level error on the USB bus.

If the affected USB device driver requires accurate error reporting to function correctly, you should not apply this hotfix. Or, you should disable the Soft-Retry functionality by setting the appropriate registry value to 0 or by deleting the Soft-Retry registry value entirely (depending on the Windows version, as described above).

A Soft-Retry process will occur when the following conditions are true:

• The registry value is enabled

• The error that is reported by the USB Enhanced Host Controller Interface (EHCI) host controller for the completed transfer is one of the following errors:
  

  • Transaction error (XactErr)

  • Missed micro-frame

  These error conditions are documented in the USB EHCI controller specification as follows: Transaction Error (XactErr). Set to a one by the Host Controller during status update in the case where the host did not receive a valid response from the device (Timeout, CRC, Bad PID, etc.). Refer to Section 4.15.1.1 for summary of the conditions that affect this bit. Missed Micro-Frame. This bit is set when the host controller detected that a host-induced hold-off caused the host controller to miss a required complete-split transaction.

For more information about the USB EHCI specification, visit the following Web site:

http://www.intel.com/technology/usb/ehcispec.htm

Data transfer rates that USB 2.0 supports

USB 2.0 supports the following maximum data transfer rates, depending on the amount of bus bandwidth that a device requires:

• 1.5 megabits per second (Mbps) for low-speed devices that do not require lots of bandwidth. These devices include mouse devices and keyboards.

• 12 Mbps for full-speed, higher-performing devices. These devices include storage devices, speakers, scanners, and video cameras.
  

• 480 Mbps for high-speed devices. These devices include mass storage devices and Hi-Speed CD or DVD recorders.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

824684Description of the standard terminology that is used to describe Microsoft software updates