[Tfug] battery life, power management and windows vs linux

[Jeremy D Rogers]

On 3/21/07, Ranjan Grover <ranjan.grover at gmail.com> wrote:
> > Just a thought, but are both operating systems accurately calculating the
> > time left, or is one over/under estimating?
>
> Tha's a very good point. The real test would be to see how long the
> battery really lasts by just leaving the computer idle till the
> battery runs out and comparing it between windows and linux.

That's true, I agree with both of you that the *real* test would be to
run the battery down and time it, but I just like booting into windows
for that long. :-)
Someone correct me if I'm wrong, but I was under the impression that
the modern 'smart batteries' do all the time remaining and charge
calculations internally and report via acpi. I was therefor operating
under the assumption that the reported charge / time remaining was
completely OS independent and based only on the current/power drain.

That said, I could see a case being made for not trusting these
semi-instantaneous values and I agree, the real test would be to run
it out on both sides.

> Maybe using a different cpufreq governer might help. I'm using the
> cpufreq-userspace instead of ondemand although I'm not completely sure
> of either's technical details. Also NTFS does not support block
> journaling whereas ext3 does, so the difference in the power could be
> the hard drive and how the filesystem interacts with it.

That should be taken care of with laptop-mode and the settings of
hdparm. My disk is currently set to spin up every 10 minutes (when on
battery) to write journalling info if there is otherwise no disk
activity required before that.

> Ranjan
>
> > -----Original Message-----
> > From: tfug-bounces at tfug.org [mailto:tfug-bounces at tfug.org]On Behalf Of
> > Jeremy D Rogers
> > Sent: Wednesday, March 21, 2007 5:48 AM
> > To: Tucson Free Unix Group
> > Subject: Re: [Tfug] battery life, power management and windows vs linux
> >
> >
> > On 3/21/07, Sean Warburton <hl2addict at gmail.com> wrote:
> > > Plug it in (or a solar panel...we are in Arizona, after all...) :) How
> > about
> > > the screen? Are there any options for toning down the brightness? Also,
> > what
> >
> > Well, as I mentioned, the brightness is set at the same level in both
> > OS's. See, my quest is not so much about getting 30 minutes more
> > battery life, but more about getting the same battery performance in
> > linux as in windows.
> >
> > > about lowering the refresh rate? (may not be much, but what if?) Also, you
> >
> > That's interesting.. I thought laptop LCD screens had fixed refresh
> > rates. After all, we're not sweeping electron beams here. I am
> > dropping the clock rate of the video card to its lowest setting, which
> > does seem to boost battery life a little.
> >
> > > may consider resolution (less pixels=less work for the computer to do,
> >
> > The res is the same as in Win.
> >
> > > right?) Also, UNDERCLOCKING!?!?!! AAAHH. Thats against my religion...If
> > you
> > > are going to underclock for an extra 30 minutes, why not save $$$ and get
> > a
> > > 1 GHz comp. The Pentium 3 class of processors goes up to 1 GHz, you
> > know...
> >
> > Well, that is the beauty of mobile processor frequency scaling. I get
> > both. I have a 1 GHz processor sitting there when I'm checking email,
> > but when I start my data analysis and need the power, suddenly my
> > clock speed doubles until the calculation is through. All that
> > automatically, I can't complain.
> >
> > >        Also, do you have one of those "12 cell" batteries, or whatever the
> > > best type is? That is supposed to give you a substantial time increase,
> > but
> > > may cost a bit. But with the best type of battery, you can get increased
> > > runtime, and possibly run it at the 2 GHz setting. Try two batteries,
> > even.
> >
> > Again, the battery life is fine, and if I'm on long flights, I may
> > well think about getting a second battery, but the quest here is to
> > find out why windows seems capable of eeking out an extra hour with
> > the same hardware and same (as far as I can see) settings.
> >
> > Thanks for the thoughts though. I may have to read up on refresh rates
> > and see if that is really fixed for an LCD.
> >
> > >        Hope that helps,
> > >             Sean
> > > On 3/20/07, Jeremy D Rogers <jdrogers at northwestern.edu> wrote:
> > > >
> > > > Well, I finally have my shiny new thinkpad t60 and I love it. Fantastic.
> > > > <excuses> Unifortunately I will  need to use some windows-only optics
> > > > software, so unlike my last laptop, I left windows installed on it and
> > > > made it dual boot.</excuses>
> > > >
> > > > Now as I've been tweaking things over the past week, I noticed that
> > > > the battery reports around 5 hours under windows and only 3.5 hours
> > > > under linux. So begins my quest. I know many things can suck power, so
> > > > I think I took care of all the usual culprits. Here is a list of what
> > > > I have working in linux:
> > > > - cpu freqency is scaling using ondemand governer (down to 1GHz from
> > 2GHz)
> > > > - disks are spinning down using laptop-mode
> > > > - wireless radio and bluetooth are off (modules unlaoded and kill switch
> > > > on)
> > > >
> > > > I did some reading up and I found out that the ati cards like my X1300
> > > > require the binarry fglrx driver to control the GPU clock scaling.
> > > > Pity I have can't use opensource, but it did help me get from 3.5 up
> > > > to around 4 hours on battery:
> > > > - gpu frequency scaled down and in low voltage mode
> > > >
> > > > Now I'm stuck. Things I've tried that haven't helped much:
> > > > - unloaded usb modules
> > > > - unloaded pcmcia/cardbus modules (or issued cardctl eject/suspend)
> > > > - unloaded modules or tried physically removing unltrabay dvd drive
> > > > - unloaded sound modules
> > > >
> > > > The ultrabay actually seemed to help a little, but overall none of the
> > > > above gained much over 4 hours.
> > > >
> > > > I welcome any and all suggestions.
> > > > JDR
> > > >
> > > > _______________________________________________
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> > >
> > >
> > >
> > > --
> > > Windows Vista Ultimate beta (build 5600)
> > > Ununtu 6.10 (dual boot)
> > > ASUS P5N32-SLI Premium
> > > Intel Core 2 Duo 6600
> > > dual eVGA 7900 GT OCs (full x16 SLI)
> > > 1 gig DDR2 PC2-6400 (OCd to 866MHz)
> > > custom Liquid cooling :)
> > > four 17" CRTs (uber widescreen)
> > > 7.1 surround sound (296 watts)
> > > 160 gig HDs in RAID 1 setup
> > > one happy gamer
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> >
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