To support USB 1.1 devices, a USB 2.0 host controller has one or more USB 1.1 compatible controllers that are enumerated as separate PCI functions by the operating system. The USB driver stack on Windows XP Service Pack 1 synchronizes the operation of a USB 2.0 host controller with the operation of its USB 1.1 compatible controllers. When the device driver for the USB 2.0 controller is updated by using the Device Manager, the controller is programmatically removed by the operating system before the driver is updated.
Due to the synchronization of the USB 2.0 controller and its USB 1.1 compatible controllers, the USB driver stack also removes the USB 1.1 compatible controllers when the USB 2.0 controller is removed. When the device driver update is complete, the USB 2.0 controller is restarted; however the USB 1.1 compatible controller remains disabled. Therefore, any USB 1.1 devices that are attached to the controller no longer function.