Information on XO-1 power efficiency

Paul Fox pgf at
Wed Nov 11 10:21:50 EST 2009

christoph wrote:
 > Hi all,
 > I've been invited to give a short talk on "Energy consumption of Desktop and
 > Notebook Computers" with a focus on the XO-1 design at a workshop in
 > Stockholm next week. The audience will mainly consist of scientists and
 > researchers working on IT topics within the context of energy consumption
 > and climate change.

i think cjb gave a similar talk last year -- he may have slides/info you
can use.

 > Now while the original goal of getting the XO-1's power consumption down to
 > 2W wasn't achieved it's still a pretty lean and efficient machine. I
 > obviously plan to talk about the choice of hardware components and MLJ's
 > display design. Another topic I'll touch upon is the wide-range voltage
 > input which allows for a variety of power sources to be used without
 > requiring further external regulation.
 > One thing I'm less sure about is the DCON because I'm don't know how
 > aggressively it is currently being used (maybe someone can shine a light on
 > this, I didn't find anything about it on the wiki or the mailing

if you enable "automatic power management", then the dcon is used
to keep the display alive while the laptop goes to sleep after
just a 1 minute idle period.  that's the only current use of the
dcon for power savings that i'm aware of.

 > list). Another question I'm interested in is what the efficiency of the
 > AC-DC adapters shipped with the XO-1 is?
 > I'm also wondering whether it makes sense to talk about some of the ideas
 > discussed in the early stages of the project (e.g. suspend inbetween
 > key-strokes which IIRC ended up not being implemented).

certainly -- you can point out that our latencies for waking/
sleeping are just a little too long (mainly due to USB device
discovery) to make that feature comfortable to use "between
key-strokes".  but the system will wake fast enough to make going
to sleep during the "reading" phase of using an e-reader -- page
flips don't have to be super fast to be comfortable (witness the
amazon kindle).  we just never implemented such a mode in the
production software.  (i've used my XO as a book reader in the
past, using powerd to set very short (15 second) suspend timeouts
when the laptop is configured in ebook format.)


 > As I said it's only a short talk (10min max.) but there's anything else
 > significant when it comes to the power consumption and underlying design
 > that I've left out above then please give me a shout.
 > Thanks,
 > Christoph

 paul fox, pgf at

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