Celeron M vs Athlon XP M & Sempron M - power usage & battery life under low load

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Hey all,

Reading the title, you might be tempted to post without reading what
I'm saying here, but please don't.

I'm looking into this matter for a friend who wants a cheapish laptop
for light usage. Obviously, performance isn't too important but things
like price, weight, and battery life are. I have a good idea on advice
based on my research but one thing I'm still not certain on is the
battery life / power usage of the Celeron M vs Athlon XP & Sempron M.
Originally, I thought the Celeron M would win no contest, I know the
Pentium M will. But then when I looked into the Celeron M I quickly
realised it wasn't just the reduced cache and clock speed, the Celeron
M also lacked Enhanced Speedstep and "Deeper Sleep".

Realising this, I've become a lot less certain. For those of you who
don't understand, although the Celeron M still has a number of the
power saving features of the Pentium M design, the lack of Enhanced
Speestep is quite significiant. The 'deeper sleep' is also somewhat
important I suspect as I understand it can result in up to 30% power
savings over normal 'sleep'. As all (to my knowledge) mobile Athlon
based processors have Power Now!, this means the AMD based laptops
will be reducing their clock speed (and power usage) under low load
whereas the Celeron M will always be at full speed (although obviously
will be able to go into sleep states). I suspect under high load and
if you force the AMD based systems to always operate at full speed,
they will def lose to Celeron M systems, especially given that the
Celeron M have a TDP of 21w whereas lower voltage AMD based systems
tend to be 25w but this seems unlikely to be the case in low load
systems. I suspect it's going to depend a lot on the load. If the
Celeron M is able to enter sleep states a lot but clock speed cannot
be reduced much for whatever reason, then the AMD based ones won't

Therefore, I would like feedback, with regard to the power usage or
battery life of a AMD based laptop (25w TDP or lower if that exists)
to a Celeron M (not a ultra low voltage one tho). Preferbly from
people who have tested this. Either via battery life of comparable
batteries or if they actually tested the power usage under low load.
Please do mention speeds, processor TDP if known, L2 cache size and
also core type if known (for Celeron M either Banias or Dothan
although I should be able to work out with other details). However,
those who have compared Celeron M and Pentium M systems (with other
comparable specs) under low load are also welcome as this should give
some idea.

Thanks all!!!

P.S. If your a Intel/AMD fanboy and have nothing constructive to add,
please don't bother to post.

Re: Celeron M vs Athlon XP M & Sempron M - power usage & batterylife under low load

Nil Einne wrote:
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Are you looking for comparisons of the power consumption for each
processor w/all other things being equal, or are you just looking for
the best laptop for the money in terms of weight and battery life for
your friend?  If it's the latter, then you'll have to consider all the
other things that require power such as the LCD screen, HD, video card,
etc.. That would make also make comparing each CPU individually kinda
pointless, since some laptops running a Celeron M might outlast one
running a Pentium M depending on the other parts it has.  The best thing
to do would be to just look at all the estimated battery life for each
individual laptop in reviews from PC World, Laptop Magazine, CNet, etc.

Re: Celeron M vs Athlon XP M & Sempron M - power usage & battery life under low load

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Hmmm, that's not so obvious, especially since the CPU isn't the
biggest power drain.

For what it's worth, at work I have a Dell X300 (Centrino, hence
Pentium M) and at home an Averatec (mobile Athlon XP-M).  The Dell
gives me 2 hours on its standard battery and the Athlon 3 hours.
Both are small laptops with 12-inch screens and both have similar-sized
batteries.  The Dell also has an optional extended-life battery
that's good for 5 hours;  the 5-hour battery sticks out the back
and adds weight but it's a good compromise, I just used it on a
trip.  The Averatec doesn't have an extended battery; I suppose I
could buy a second 3-hour battery and figure out a way to carry it
safely on trips.

Also, the Dell's 2-hour battery charges very fast.  It's possible
that the reduced capacity is a design trade-off to buy charge speed.

Overall, it's pretty hard to say which laptop has the better
battery life.

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I suppose that's bad, but in view of the above I recommend
googling the web for reviews of Celeron M laptops if you want
to know about battery life.

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pa at panix dot com

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