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When you use a single USB bulk storage device (for example, an iPhone) with a Windows-based computer, the device appears unresponsive. This issue may occur when the following conditions are true:

  • The computer has a chipset from the Intel 5 Series or the Intel 3400 Series families of Intel chipsets.

  • The USB device has pending control and bulk traffic.


This issue occurs because the Platform Controller Hub (PCH) cannot resolve which traffic type is a priority. Therefore, the port that is associated with the USB device stops responding. This issue occurs when the processor is in the C0 power state for a long time. For example, Cx states are not enabled, or system traffic prevents the system from leaving the C0 power state. If Cx states are enabled, the device may recover a short time later.

Note This issue only affects a limited number of USB devices. The issue only occurs if the USB device driver programs the Nak Count Reload bits that are defined in the EHCI Specification for USB Rev 1.0 to 0.


To resolve this issue, contact the computer manufacturer or the motherboard manufacturer for an update to your system BIOS.

For information about your computer manufacturer, visit the following Web site:

More Information

For more information about how to identify an Intel chipset, visit the following Intel Web site: more information about Intel 5 Series Chipset and Intel 3400 Series Chipset, visit the following Intel Web site: third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

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