XO power management

Richard A. Smith richard at laptop.org
Thu Mar 24 10:54:14 EDT 2011

On 03/24/2011 10:41 AM, Ismael Schinca wrote:

> I'm planning to use different XO's, all of them 1.0 hardware. I
> definately won't be able to finish today because they all have different
> OS images and I think it would be best if I update them all (even for
> future tests). Maybe tomorrow, maybe monday.

Yes certainly please use the same image on all of them.  If you have to 
install software then please use the latest version of olpc-pwr-log.  I 
have it attached to this mail.

> I think it will be very hard to perform the same test under the same
> conditions as you suggest because:
> - It will be very time consuming (though it doesn't need a lot of
> attention during the test)

My goal is to automate the test and use a very short test window.  ie 20 
minutes or so.

> - The air conditioning in our building is quite frankly chaotic so
> temperature is really variable (which is actually a lot worse for us
> humans than batteries ;) )

Yes. Sorry my use of the word exactly was probably too strong.  I don't 
mean that it has to be 25 degC ambient and only that temperature.  The 
temp fluctuations in a air conditioned office should be within reason. 
I just don't want the profiles generated in an office and then the test 
run in a outside warehouse at 33C.  Or the curves generated on a XO-1 
with build 8.2 but the test run on a 1.5 with build 10.1.3. That sort of 

> The closer I might get, which I think could be pretty close is:
> - Install the SAME fresh OS image and firmware version on all the test XOs
> - Disable power management in every XO.

and dpms. xset -dpms from the sugar terminal other wise the screen will 
turn off in 20 minutes and change the power draw.

> - The laptops batteries are mostly charged, so it will be a charge after
> discharge, so I think temperature there is less of a concern
> - Run the tests at the same time in every XO

Yes.  I believe that will work fine.

Note: I'm getting on a plane in a few minutes so this will be my last 
e-mail until much later on today.  Possible tonight or tomorrow.

Richard A. Smith  <richard at laptop.org>
One Laptop per Child
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