Microsoft has fixed the battery drain bug that has been affecting a number of computer owners with Intel Core Duo-based notebooks. However, two of the three causes of the drain are not fixed by a patch posted by Microsoft yesterday. The patch fixes faster-than-usual battery drains arising from the CPU's inability to enter Advanced Configuration and Power Interface (ACPI) processor idle sleep states as a result of the USB 2.0 driver leaving "the asynchronous scheduler component running continuously". However, the patch doesn't prevent the USB host controller from finding itself unable to shut down when devices are removed from nested USB hubs, or when said controller is hooked up to USB 2.0 devices that make use of its periodic scheduler. Both instances can also cause the exceptional power drain, but neither are fixed by the patch.