ACPI C3 "Deep Sleep" processor state with X21

[Terrahawk]

Hi everyone,

I have a tricky question here.

It has to do with trying to get the most battery life from my X21. Normally, it sits nicely between 7-9W when idling while using the battery. However, once I insert my Sierra Wireless Aircard 580 (it appears as a Lucent USB Open Host Controller) the power uage shoots up to between 15-17W while idling, and that's just when the card is inserted, and the wireless connection is not initiated.

I would be quite happy to accept that as a fault of Microsoft's small USB 2.0 scheduler bug that stops CPUs entering the ACPI C3 "Deep Sleep"state but the X21 does not have USB 2.0 (even though the AirCard could be showing up as a USB 2 controller which would explain that away). However, using the same card with the same drivers on my R40 has a markedly different effect, in that the power usage is only impacted slightly - the R40 idles between 8-9W and with the AirCard inserted, it idles at about 10W. I understand that there are different chipsets et cetera between the X21 and the R40, but surely they do not have a "P3 don't use deep sleep" and "P-M feel free to use deep sleep" specific code path in the same driver file?

I can see the ACPI processor states using perfmon.exe and with no cards in the CardBus slot, the C3 "Deep Sleep" state is entered for over 90% of the time. With the AirCard in, the C3 state is never entered and the C2 "Stop Grant" state is entered 60% of the time, with the other 40% unable to be found by me. This has the effect of doubling my power usage and raising the CPU temperature markedly.

Does anyone know exactly why this happens and how I can fix it? Both the X21 and R40 are running Windows XP SP2 and have the so-called patch for the USB2 scheduler "bug" installed.

Thanks,