Battery Drain on x61 Tablet

[pibach]

I posted this already here http://www.gottabemobile.com/forum/foru ... p?TID=4697 but maybe this is the better place to get an answer:

The x61 tablet I own has similar specs as its non-tablet brother, the x61s and I would expect both to have same power consumption if both are used in laptop mode.

As a colleague of mine has the x61s, I could do direct comparisons. And for some weired reason, his machine needs ~2 Watts less than mine at the same settings/usage, both running Vista. Also posts in this forum indicate that the tablet version is consuming more power. Why is that? Is it the pen/Wacom needing 2 Watt? The rotation sensor? Or something else?

I installed Linux (Xubuntu 7.10). With "PowerTOP" you can track down the power consumption to every single process. And there, x61t and x61s are consuming exactly the same power under Linux! With some tweaks (2.6.24 kernel and module unloading) I got 7,8 Watts on an idle desktop at minimum brightness, i.e., 2 Watts less than I get running Vista. My colleague gets his x61s down to 8 Watt running Vista. The pen/Wacom digitizer does not seem to consume significant power if not in use.

So I suspect this 2 Watt x61s vs tablet difference to result from some software bug in Wacom/Vista. Or does anybody have an explanation for this magic power drain on tablets? Does it occur on other Vista/Wacom tablets or only on Thinkpads?

[fbrdphreak]

The digitizer and all associated hardware to make the tablet input work draws more power, period.

[donzoomik]

Well, it might consume more power, but not that significantly.

I'm also experiencing increased battery consumption on my X60 nontablet with Windows Vista. I reinstalled it several times, but i haven't yet been able to achieve stable consumption of 7,5-9W from first install. Now i cannot force the consumption to drop below 11W. Battery life has dropped from 8h+ to 6h max. This is significant loss, as i bough X series for extra battery life.

Aero disabled, Power management tuned for maximum savings...

I can't really think, what is hogging power, as CPU is sitting idle at 1-3% with Task Manager, no disk or network traffic.

I should service it anyway, i'm experiencing whine from the laptop, WLAN card area, that might point to faulty motherboard or WLAN card eating away all those watts.

I'll investigate further with pointed PowerTOP tool.

[pibach]

I suspect the Wacom driver over serial to have some misconception and won't let the CPU sleep. Using Linux however, this works without power drain (switching the Display off I get 6,4 Watt idling and 99% C3 sleep state with <10 Interrupts/sec).

Maybe one could investigate this in Vista by removing the serial interface and Wacom driver completely? Or the power supply for the digitizer? Any idea how to do this? Unfortunately there is nothing such as PowerTOP for Vista. Great tool!

[pibach]

Have a suspect, might be the AHCI mode not implemented/working properly under Vista.

www.lesswatts.org:

"SATA Aggressive Link Power Management
Several SATA controllers, that use the AHCI specification, have a feature called ALPM, which stands for Aggressive Link Power Management. ALPM is a technique where the SATA AHCI controller puts the SATA link to the disk into a very low power mode when there's no IO for awhile. The controller automatically puts the link back into active power state when there's real work to be done. This can save between 0.5 and 1.5 Watts of power."

[pibach]

...WLAN card eating away all those watts.

Did you check WLAN power savings mode in device manager? Vista, other than XP, does set this per default to no power savings due to compatibility issues with older routers.
If set to power savings, WLAN off versus on is only a 0.1 Watt penalty at my x61t (without file transfer).

[pibach]

The digitizer and all associated hardware to make the tablet input work draws more power, period.

We have measured that and it is negligible. The digitizer power consumption in Laptop mode is less than 0,1 Watt.

[smaug]

How much RAM is there? Mine never drops below 10.5W but I also have 4GB of RAM. Could that be it?

[ducky2802]

Could be the sxga+/xga+ screens, which for some reason, seem to be rated at higher nits... 185 vs 150 for standard xga, 190 vs 180 for sxga+ to UL, and 150 for mt+mv, though many users say the mt+mv is about as bright as the sxga+.

[IvanAndreevich]

I'd like to raise this from the grave. What's the minimum idle power consumption that anyone has ever achieved on an X61T?

I'm at around 8W (least I've seen is 7.7W momentarily) with an Intel X25-M G2 SSD - that's completely idle, no wireless, fan is off, minimum screen brightness, battery stretch enabled.

This is still quite a bit higher than my X61s under the same conditions! It also sucks that the tablet only has a 67AH battery, while the X61s has 75AH. Result? Easily 10 hours+ on X61s at idle vs 8 hours on the tablet.

[IvanAndreevich]

I'd like to post some preliminary findings.

Basically it may be the SXGA+ screen. I checked out an X60T with an XGA screen, and it was 6.5W idle! Now I need to get my hands on an SXGA+ X60T and swap in the same hard drive to see the difference between the two different screen resolutions.

I will also compare the X60T vs X61T, both with SXGA+ screens.