pavelmachek ([info]pavelmachek) wrote,
@ 2006-07-31 01:54:00
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USB sucks
First I thought it is Linux that sucks. We did some quick measurements
with AC ampermeter; Windows ate 10W at minimum backlight and Linux ate
-- wait for it -- 15W during installation, 17W during runtime. Ouch.

(To put it into perspective, that means 7.5 hours with extended
battery on Windows, versus 4.4 hours with Linux/GNOME).

I promptly deleted both Windows and GNOME, but still, on console, with
self-compiled kernel, I was getting power consumption in range of
14.6W (5.1 hours). I started to investigate WTF is going on... then
realized I have this small fingerprint reader on USB.. and that
probably forces USB to stay on and wastes power.

And yes I was right. USB removed, and we are down to 11W (6.8
hours). So what does USB suck? 2 hours of my battery life...

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yeah, powering USB can make a huge difference
(Anonymous)
2006-07-31 01:34 am UTC (link)
I have an iAudio X5 mp3 player. It's sold as having 14 hours of battery life, and I think I could get at least 11 hours from it. But I mostly bought it because of Ogg Vorbis support.

Then I switched to the much more powerful (and, well, open-source ;-)) rockbox (www.rockbox.org) firmware for it.

The firmware was great, but I only had 6 hours of battery life. For many people, that would be a killer argument against.

However, recently a patch was added to CVS, that gives me a whopping 15 hours of battery life. The patch powers down the USB OnTheGo port. Maybe it also powers down the FM radio receiver, but the USB OTG chip was definitely the huge power waster.

Linux could definitely use some work in power management. I havn't found a reliable way to power down my (hostap) wireless...

(Reply to this) (Thread)
Re: yeah, powering USB can make a huge difference
(Anonymous)
2006-07-31 09:46 am UTC (link)
Windows XP with issues with ACPI Drivers saw similar issues on Centrino Core Duo platforms where if there were devices attached to the bus it wouldn't shutdown the USB even if they were inactive. Unfortunately most modern laptops have at least a couple of USB devices permanently attached. Mine has a SmartCard reader and BT Dongle builtin, and alot are coming with other things such as cameras and flash memory readers attached to USB too.

I know the OLPC project is looking for some serious power management stuff so the device takes as little power as possible shutting down everything that's not in use. There's patches on their list for sound etc so hopefully once they're done its just a matter of porting all the drivers.

(Reply to this) (Parent)
Is it sufficient to unload the modules?
(Anonymous)
2006-07-31 09:28 am UTC (link)
Until proper power-down of USBports is implemented, is it sufficient to unload the ?HCI modules to power down the hardware?

(Reply to this)

T43 fingerprint reader
(Anonymous)
2006-07-31 10:14 am UTC (link)
I have a T43 with fingerprint reader, and I use the vendor provided driver at the minute. Could I save some battery life somehow or would I have to remove all USB support?

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(Anonymous)
2006-07-31 06:48 pm UTC (link)
See also http://web.glandium.org/blog/?p=85 for some similar experiences.

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(Anonymous)
2006-08-01 12:54 pm UTC (link)
also 2 last paragraphs here:

http://lwn.net/Articles/191652/

"The last update came from Len Brown, who discussed the power management summit..."

(Reply to this)

power graphs
[info]hughsient
2006-08-05 08:50 am UTC (link)
Hey,

I've found the graphs in g-p-m (http://www.hughsie.com/applications/Coppermine/thumbnails.php?album=9) show how much you can save -- for me I can save 5W of power turning my brightness from max to min and a similar amount when I turn off wifi.


Maybe something to play with.

Richard.

(Reply to this) (Thread)

[info]beckysedaz
2008-07-17 02:07 am UTC (link)
 If you drive to work, you can save the same amount of energy by carpooling just once as you would save changing one incandescent bulb for CFL for a year.

(Reply to this) (Parent)(Thread)
Wow!
(Anonymous)
2008-08-11 10:28 pm UTC (link)
Wow! You can save an entire car trip's worth of energy by replacing just one bulb for a year? Now I'm totally going to change all my bulbs! That's like an entire tank of gas that I'm saving per year. Thanks Becky for the tip! Now I wish carpooling was that easy to switch to...

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