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Thursday, May 18, 2006

Power Drain "fix" from Microsoft

Just Yesterday Microsoft released a patch to fix the battery power drain in Windows XP SP2-based portable computers:

This problem may occur if one of the following conditions is true:


• The portable computer cannot enter the deeper Advanced Configuration and Power Interface (ACPI) processor idle sleep states.

This occurs when the USB 2.0 driver leaves the asynchronous scheduler component running continuously. This prevents the processor from entering the deeper ACPI processor idle sleep states, or C-states. C-states save power when the processor is not busy. These states range from C0 to C3 or C4. Typically, an idle portable computer uses the C3 and C4 states to preserve battery power. If an idle portable computer cannot enter or maintain the C3 or C4 states, the battery power drains more quickly. This problem is fixed by installing the download that is available in this article.

• The USB host controller is unable to turn off.

This typically occurs when devices are removed from a nested USB hub that is attached to the host controller. The host controller does not recognize the device removal. Therefore, the controller is never turned off. This prevents the processor from entering the ACPI processor idle sleep states. This problem is not fixed by installing the download that is available in this article.

• The USB host controller uses the periodic scheduler for USB 2.0 devices.

This typically occurs when devices that rely on the periodic scheduler are attached to the host controller. These may be isochronous (Isoch) devices such as audio devices. Alternatively, they may be interrupt devices such as mouse or keyboard. This problem is not fixed by installing the download that is available in this article.


The bad news is that I tested it and it does not work or fix anything in our eos. The problem is that the eo WiFi and BT adaptors are USB devices. If you read what Microsoft is saying about this issue you will easily see that in our case the USB Controler is never stopped because those adaptors are simply never removed from the eo. As result the Periodic Scheduler is never stopped and that prevent the processor from entering in C3 or C4 stage. Microsoft's solution forces the USB Scheduler to be stopped if the USB device is removed, in our case Microsoft together with VIA needs to find a way to decrease the USB periodic scheduler for USB 2.0 devices to let the proccessor enter the C3 power stage at least. So basically, we are in the 3 group where Microsoft says:

• The USB host controller uses the periodic scheduler for USB 2.0 devices.

This typically occurs when devices that rely on the periodic scheduler are attached to the host controller. These may be isochronous (Isoch) devices such as audio devices. Alternatively, they may be interrupt devices such as mouse or keyboard. This problem is not fixed by installing the download that is available in this article.


Anyway... the patch can be downloaded here.