|The ThinkPad system cannot enter C3 or C4 power states, resulting in increased power consumption and shorter battery life.|
The following ThinkPad systems may be affected by this symptom: Download the Microsoft patch from document KB918005, http://support.microsoft.com/kb/918005.
The symptom 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 laptop uses the C3 and C4 states to preserve battery power. If an idle laptop cannot enter or maintain the C3 or C4 states, the battery power drains more quickly.
The power states are defined as follows:
- C0 - full power
- C1 - auto halt
- C2 - stop clock
- C3 - sleep (suspend)
- C4 - deep sleep (hibernation)