T60 USB2 devices cause high power draw (PIC)

[Zender]

Hello everyone,

I would like to ask a few kind souls to help me determine whether anything can be done about a bug in Windows XP SP2/SP3 USB drivers.

I've run into an issue with USB2 devices causing the computer to draw more power than it should. This happens in Windows XP SP2 and SP3. Microsoft has acknowledged this problem, but only fixed it partially (you can see three possible causes and only the first is addressed by that hotfix).

The bug prevents the processor from entering low-power C3/C4 sleep states. You can actually hear whether your machine uses these power-saving states - ever heard of the buzzing/chirping sounds CoreDuo is notorious for? An example of how weird it is. During the tests I had wifi on and screen to 4/7 bars, max. battery life profile, machine from my sig. EC reader is ExpressCard memory card reader, which connects to the USB bus - I connected it to the machine, and disabled in device manager, so that's why "off" in the beginning. The numbers are a little rounded, but at most 0.5W.



The last line proves that the device does not in fact need the power, it's caused by ineffective USB power management. Well, what to do now... I'd like to know whether anyone with T60 and Windows XP is not affected by this problem. You need at least Bluetooth, to have some common ground, and then possibly WWAN or some external USB device, though hard drives not preferred (these really need some power). Also would be glad to hear from Vista users, whether it's better there, even though I'm definitely not switching.

Please check whether you have hotfix KB918005 installed. Add/Remove Programs, check Show Updates, under Software Updates, there it should be listed. Please tell us whether you have custom Windows installation, or are using preload. To see current power draw, you have to be running from the battery, double click battery gauge in taskbar, switch to Battery Information tab, there's "Wattage" - always wait a while for it to "settle".

Reboot. Switch to max. battery profile (or at least don't have max. performance), disable all radios (Fn-F5), and check the power draw. Enable Bluetooth - does power draw change? Connect some other USB(2) device - does power draw change? Disable the connected device in device manager. How is it now? Disable BT. Are you back where you started? You can also check whether it's good or bad by listening to the computer - do you know about chipset buzzing/chirping sounds CoreDuo is notorious for? If you can hear them, the processor is actually entering low-power C3/C4 states.

I would like to thank everyone who actually reads this, and everyone who makes some time to check and post the power draws here.