First!?

Surely SpeedStep (or CoolNQuiet) is a better solution than arbitrarily throttling the CPU?

If I throttle my CPU to 50%, thus doubling the battery life, but I'm doing something CPU-intensive, so that my task takes twice as long, then I'll still get the same amount of work done before my battery gives out.

Yeah, I know my numbers don't work. Is there anybody out there with reliable figures for the trade-off?

> Surely SpeedStep (or CoolNQuiet) is a better solution than arbitrarily throttling the CPU?

Any modern laptop in the last 2 years already has SpeedStep / CoolNQuiet enabled. This is a constant, a default, it is always there -- even for desktop systems. The power usage you see above is WITH that enabled. It's standard.

Download CPU-Z and watch your CPU multiplier (and thus clock speed) change in real time with CPU load:
http://www.cpuid.com/cpuz.php

> If I throttle my CPU to 50%, thus doubling the battery life

This will only double your battery life if you're actually at 100% CPU usage all the time. That would be.. extraordinary, particularly on battery. For most use cases, your CPU will be idle the vast majority of the time.

The reason to throttle the CPU, as I said in the post, is to not have to worry about unusual peaks in CPU usage. Let's say you happen to visit some web page with a horribly coded flash advertisement that uses 100% CPU time .. do you want to watch task manager, see the unusual CPU usage, and manually close that web page? Or do you want the system to automagically throttle the web page's CPU usage back to a reasonable level for you?

Also, understand that the CPU throttle does not actually disable a CPU core. A throttle of 50% means neither core can never be above 50% usage. Tasks will still be dispatched by whichever CPU core is available, so you get all the benefits of a dual-core chip, just a "slower" one.

But seriously, thanks for the highly informative article... I revisited the "The Cost of Leaving Your PC On" too, which has caused me to rethink my whole server-on-24/7/365 setup I got going.

Also, for some folks, myself included- lowering the brightness in the display for power consumption reduction is just not going to happen, for a number of reasons such related to their eyes. But not watching a DVD or graphics intensive application should become a no-brainer for non-intuitive users over time.

Would be interesting to see these stats with Aero turned off. Or at least the GPU one. I suppose the differences are small, but if one wants to save power then turning off Aero could give some extra time.

I like the way kubuntu handles my laptop. It generally throttles down to 800Mhz unless theres actually a high sustained usage (startup etc). This way you have the power if and when you need it. And it automatically dims the screen a bit when disconnected.

I find dual cores are alot more responsive even on low power, even including when I'm using eclipse, which uses a fair amount of resources.

> I suppose the differences are small, but if one wants to save power then turning off [Vista's] Aero could give some extra time.

This is a myth: Aero makes no difference whatsoever.

http://techreport.com/discussions.x/10945

--
In all, none of our configurations consumed more than an additional watt moving from Vista's Classic to Aero interface. Power consumption did spike by between 10 and 15W when using Aero's 3D window switching feature, though. This spike didn't last for much more than a second, so it's unlikely to have a significant impact on overall system power consumption or noise levels. In fact, none of the cards we tested with variable-speed cooling fans even ramped up their fan speeds during our Aero testing.
--

> I like the way kubuntu handles my laptop. It generally throttles down to 800Mhz unless theres actually a high sustained usage (startup etc). This way you have the power if and when you need it

To be clear, all modern operating systems do this-- heck, even ancient crusty old circa-2001 Windows XP does it. As long as you have a CPU built in the last 2-3 years which supports dynamic clock adjustment. It's quite standard..

Honestly, there's no point in using any sort of "power saver" mode. Processes that run will still run, but take longer to do so. If you have a process that takes 10s normally, and 20s with the CPUs throttled at 50%, what have you gained?

Of course, you need to have more fine-grained data to answer this question, but I have a feeling that the answer will be "not much".

The only real result of using power savings mode is waiting longer for your computer to do the things you want it to do anyway, hence negating the power savings.

If you want to reduce CPU power consumption, run less processes.

/Mike

@Mike:
That theory doesn't necessarily work, because power is not consumed linearly based on increased work.

In addition, increasing the power consumed in the laptop has a net effect of increasing the heat generated, which will cause the fan to run longer, hence using more battery power.

Only wimps use Core 2 processors. Real men use Pentium 4s in their laptop. Real men have fried testicles :P

Humour apart, I've got a P4 Prescott with HT on my laptop. Do you think HT being turned on/off affect battery life? I've not been able to quantitatively measure, but would assume that with HT on, each hyper-thread is in a way throttled to 50%. Would this help battery life in the case of your horribly coded Flash ad?

Windows Vista already turns off the Aero translucency effects when running on battery or in Power Saver mode anyway.

@John:

As I mentioned above, I'd be interested to see some more data about this. From what I've seen, the power consumption for the different P-states is almost linear.

With CPUs that support something like Intel's Speed Step technology, an explicit power mode setting isn't very useful. You get low clock speeds when browsing the web, and the full attention of the CPU when, say, resizing that image or compiling.

(Yes, I use my ultra portable for software development on the go quite a lot)

/Mike

@Jeff:

>> I like the way kubuntu handles my laptop. It generally throttles down to 800Mhz unless theres actually a high sustained usage (startup etc). This way you have the power if and when you need it

> To be clear, all modern operating systems do this-- heck, even ancient crusty old circa-2001 Windows XP does it. As long as you have a CPU built in the last 2-3 years which supports dynamic clock adjustment. It's quite standard..

I think you misunderstood what he tried to say, the default behaviour with Windows is to increase clock frequency "immediately" (within a few milliseconds) to the maximum as soon as something uses 100% CPU (at least last time I checked, I always used SpeedSwitch XP to force the lowest speed in battery mode - the advanced settings never worked right for me), whereas under Linux you can configure things to e.g. only switch to the next higher clock frequency and only after at least 4 seconds of > 80% CPU usage or similar things (though I have no idea what the default configuration for this is under Kubuntu).

Is there an alternative for "Kill A Watt" to use in 220-230V AC?

> Let's say you happen to visit some web page with a horribly
> coded flash advertisement that uses 100% CPU time ..

AdBlock and NoScript are essential tools, even when you're not trying to conserve your battery power. Doubly so when you are.

The urban legend, that a LED backlit saves energy, is disproved with your measurings.
So why pay the extra fee for an LED-backlight than?
Only for the little savings in weight (which correlate with some mechanical instability)?

What about using the built-in speakers at various levels? I know for handheld games, you can extend the battery life quite a bit by using earbuds or turning the sound off/down.

And this is why I use a laptop as my local 24/7 "server" (which doesn't do much other then keep open IRC for logs and uTorrent). You just can't beat the power savings compared to leaving my desktop on all night.

My home desktop Core 2 Quad runs 100% constantly crunching numbers for uFluids@home. Just that in an of itself could be using over 100W!! 24 HOURS A DAY!!!

Just some suggestions for the graph in your blog:

- Add a legend saying what the colors are (yes, I know that information is in the text).
- Instead of two bars showing minimum and maximum power draw, have one stacked bar.
- If you still have the old laptop (or the power data from it), put a second series of data points showing its power draws for the same things.

Dave Lessnau

Are the numbers at idle broken down by component? Or are the all for the same idle?

If they are the for the same idle, you could grab nircmd:

http://www.nirsoft.net/utils/nircmd2.html

and at least separate the lcd out from the rest of it, with a command like:

nircmd monitor off

> This is a myth: Aero makes no difference whatsoever.
> <a href="http://techreport.com/discussions.x/10945">http://techreport.com/discussions.x/10945</a>

The results may still apply but it's interesting to note that they only tested desktop computers and graphics cards, so laptop hardware may be different.

With these results, it makes more sense than ever to undervolt the CPU.

http://en.wikipedia.org/wiki/Undervolting

Undervolting requires some detective trial-error work, but once done, works like a charm reducing power consumption without affecting performance.

I use Notebook Hardware Control to undervolt my Centrino Pentium-M with success, but it seems the software is not being developed anymore, and I still haven't been able to make it work with the Core 2 Duo CPU based laptop I use at work.

Somewhat related side topic: If I want to watch movies on the plane, and maximize my battery life, is there an alternative to using the DVD drive?

Can I rip a movie to disk like I can my CDs? Is any software tool that does this illegal?

How much battery life am I really saving? What's the trade-off on disk space?

I guess a larger question, looking at Jeff's graph:

If I rip a DVD movie to disk to save battery, how much is the CPU usage going to increase to decode the file for viewing? Does that make up for the gains not spinning up the DVD drive?

BradC, the video will be decoded by the GPU/CPU regardless of the source, computer dvd drives have no decoding capabilities, much less laptop ones.

Your best best will always be to rip the dvd to the hard drive.

I've found Vista on a laptop kills battery so power consumption must be higher - exact same hardware with XP gets me an hour longer. All drivers up-to-date etc...

Who knew that a solid state drive used so much power?

Any info on the difference between that and a regular 2.5" drive?

titrat: Jeff's old laptop had a 12.1" LCD for which the difference between max and min brightness was 4W. His new one has a 13.3" LCD for which the difference between max and min brightness is 3W. I make that a factor of 13.3^2 / 12.1^2 * 4/3 ~= 1.6 in backlight efficiency.

Of course that's pretty bogus, because (1) the measurements are only accurate to ~ 1W and (2) we don't know how the actual brightness levels compare and (3) we don't have a comparison to the situation where the display isn't lit at all. So Jeff's figures don't exactly justify saying "see, LED backlights are better". But *if* you insist on using them to try to tell whether LED backlights are better, such little evidence as there is suggests that they are.

> BradC, the video will be decoded by the GPU/CPU regardless of the source, computer dvd drives have no decoding capabilities, much less laptop ones.
> Your best best will always be to rip the dvd to the hard drive.

A quick search tells me that in the United States, using any software that can bypass the security restrictions of a DVD is illegal, even if you are only using it for personal use.

Bummer.

Another variable to test is WiFi transmission power. Wireless cards turn down the transmission power when they receive a strong signal from the base station. Your wireless driver may allow you to override this (I know you can do this in Linux) for testing purposes.

>BradC, the video will be decoded by the GPU/CPU regardless of the source, computer dvd drives have no decoding capabilities, much less laptop ones.
>Your best best will always be to rip the dvd to the hard drive.

Sure, it would be the same if I rip it in the original MPEG2 format, which will take up 6-8GB of drive space.

I was referring to a transfer to MPEG4 or something more modern, like Jeff describes here:

<a href="http://www.codinghorror.com/blog/archives/000170.html">http://www.codinghorror.com/blog/archives/000170.html</a>

So the comparison is: MPEG2 from DVD drive -vs- MPEG4 from Hard drive. I'd be interested to see a power-use comparison of those two scenarios, since the MPEG4 is very likely to use more CPU.

If you're running a linux laptop, you can see which processes use the most amount of power by using the lm-sensors package and running lm-profiler.

i have (and had) a very good experience with my battery. i bought a dual core dell in august 2006, and since than my battery dropped only to ~90% which not what I can say about most of the batteries.

the most important trick was to remove the battery when AC is plugged. the *heat* kills the battery (there is an wikipedia article on LiIon batteries, read it).

second, i configured my laptop to have the lowest consumption possible when running on battery. disabled one core, disabled bluetooth and wireless, decreased the voltage of my ati card (aticonfig --set-powerstate=1), decreased laptop's backlight. powertop reports around 15.5-16W consumption in idle mode. last time my laptop survived 2h40min without recharging.

Well, my laptop uses a whopping 120W when running a little more than idle. I've haven't tested it when running a heavy 3D app or anything, but I'd suspect it to go up quite some.

Ah well. That's the downside of having a laptop that can run circles around the average desktop...

I have the same laptop, just 64GB SSD instead of 32 and 3GB of RAM.

The power use overall of this laptop is noticeably better than any other laptop I've used. I use this laptop at conferences when speaking, and I no longer bother plugging in the AC adapter - the 9-cell better will last me 3 sessions before I'll switch to the 6-cell. I use video and audio in my talks, and run 3 watt USB powered speakers off of the laptop as well as running CamStudio to record the session.

The laptop has a wireless "kill switch" I use if I know I have no need of bluetooth / wifi / cell access - throw the switch and the laptop turns off these components. Not only is this cool for power use, but also I have this fear one day some hacker will use wifi to mess up my session. I didn't say the fear was rational. Add the kill switch to the "single core" mode and the battery time is impressive to say the least.

Oh, I'm also loving the fact, for science, you defragged your SSD =p

My laptop is lucky to get 30 Minutes....

Time to buy a new battery i guess.

BradC, despite the legalities of ripping DVDs there are dozens of commercial softwares that do it legally, so it's a rather moot point.

MPEG4 does use slightly more CPU resources, but on a modern high-end CPU like this, usually not enough to bump it to the next power state. Rips are generally cropped & resized as well. MPEG4 AVC however does stand a good chance of using enough CPU to lower battery life. MPEG2 DVDs actually use quite a bit of power because they're so much higher bitrate than most MPEG4 rips; it takes significant CPU to parse & decode the stream, plus at low bitrates cpu-saving skips are more common.

However, if you can get your graphics card to do the decoding of anything, power use will plummet. They're amazingly good at that.

Interesting thing to point out. On linux, starting from kernel 2.6.23 (for x86) and 2.6.24 (for x86-64), there is new tickless mode: mode, in which CPU is being idle much longer than in regular modes. Basically, even when CPU is idle, OS programs PIC (Programmable Inerrupt Controller) to wake up CPU (to check whether there is something to do) 100 times per second (for Windows frequency of wake-ups is 100Hz, for linux &#8212; from 100Hz up to 1000Hz). In tickless mode, unneeded interrupts are not scheduled, and CPU is _really_ idle, which helps conserve power.
BTW, Intel has utility powertop for linux that can be used to diagnose power consumption.

Has anyone done any testing to see if a perpetually plugged-in laptop uses power to try and charge the battery occasionally? Would it make sense for an at-home worker to remove the battery when it's plugged in?

If you're truly environmentally conscious then almost any laptop will beat the pants off a desktop in terms of power usage. Although the same laptop will be more expensive, the difference is getting smaller and smaller each year. And who knows, maybe we're already at a point where the difference in power consumption (price for the power) is equal to the difference in price of the hardware...

If nothing else you save energy. Running a 600W power supply all day is much more expensive than a laptop.

check out the Vista Battery Saver, it'll automatically put you in the most efficient power plan.

http://www.codeplex.com/vistabattery

jas

Stephane: Just to be clear, you do realize that the "600W" on a 600W power supply doesn't mean it draws 600W, right? That number is the peak output -- normally, both the output and the input will be a lot lower than that. (Still not negligible, though.)

>To be clear, all modern operating systems do this-- heck, even ancient crusty old circa-2001 Windows XP does it. As long as you have a CPU built in the last 2-3 years which supports dynamic clock adjustment. It's quite standard..

I have a machine I built back in 2006 which has an A64 X2 4400+ in it, it's a CnQ capable chip. XP and Vista both refuse to scale the chip, without use of trial software from AMD's website. [K]Ubuntu automatically scales the frequency on my chip.

In most cases, only laptops and lowend builds force SpeedStep/CnQ, if you pay the premium for a high quality rig or top-notch processor, it's expected that it will run at it's rated speed constantly.

I have to ask, why spend money on a kill-a-watt when your acpi will happily report that data when on battery? The aforementioned powertop lists that data, and GNOME power manager will even graph it out over time for you.

I haven't spent much time fiddling with Vista power management -- did they fix that mess that was XP's power management much? XP did indeed do CPU throttling, if you set it to the counter-inuitive "minimal power management" mode. Are they minimizing power, or management?

It's interesting to see with all that low power hardware that my laptop's not using much more power. At times, I've gotten it down to around 14W, which I don't think is too shabby.

Throttling is not always a clear win. According to the Intel Linux power optimization guys, the way to saving power is a race to idle. That is, when you have some work to do, the most efficient way is to do the work as fast you can and then turn off everything you can. By being able to influence the whole software infrastructure, open-source platforms can leverage this by coordinating wake-up times to take care of all the backgroundwork in a single power-up cycle. User unfriendly programs, such as flash advertisements, of course ruin this by breaking the premise that all the work to be done is actually useful. Ignoring this there are actually huge power reductions to be reaped in the x86 platform by coordinating sleepcycles. 99% of the time most of your laptop can be asleep, only the backlighting and minimal power to handle activity on wireless and input devices needs to be active.

Regarding LED backlights, they just need their time - current LEDs still aren't significantly more efficient than cathode tubes. But given the trends, the tubes will be history soon.

'Turn down the screen brightness'

This here should be a universal truth for all electrical devices (gadgets). I few times I have chatted to people who have recently got new phones, only to hear them complain about battery life.
I grab the little buggers, hit settings, and take the brightness down nice and low. As all phones I have seen default to 100% brightness. Note I have worked with a decent selection of handsets, as I did some mobile game porting straight out of Uni.

This was one of the 1st things I did to my SE k608i - cranked it straight down to 50%. I still get to 3-4 days battery life on the original battery. Probably one of the main reasons I have had the same phone for more than two years. While I don't make a lot of calls, I do manage some games of solitaire in now and then.

THANK YOU for this. We live off the electrical grid and use an inverter/battery set up with solar in the summer and generator charging in the winter. We bought my current computer 5+ years ago, *two weeks* before we found out we were moving off grid. I work from an old log cabin in the Idaho mountains, so my computer runs about 12 hours per day.

My 2.4ghz box with a 19inch CRT just EATS power, and I was trying to justify the cost of a laptop...you just did. lol - and I only started looking for info today!

(Yay! I get a new computer! lol)

Thanks,

Julie

"Throttling is not always the answer"

Thats true, IF you care about whatever calculations are being done, and they're not being done in a spin loop. If the program doesn't yield/sleep and doesn't terminate without user input, race to idle won't help. I don't want to deflate powertop's efforts, but the timer issue is premature on the laptop. There's other, more high profile problems facing Linux power management, like redesigning suspend and hibernate so they work every time. It's nice that powertop suggests other measures like powering down unused USB, though.

"Has anyone done any testing to see if a perpetually plugged-in laptop uses power to try and charge the battery occasionally? Would it make sense for an at-home worker to remove the battery when it's plugged in?"

Yes, when the battery drains itself to 95% and the BIOS decides it's time to recharge to 100%, it uses power -- and it shortens the battery life. If you keep the laptop on AC most of the time, you want to remove the battery most of the time, and do a refresh cycle on the battery once a month.

Those of you who leave laptops turned on 24/7 should know that standard laptop hard drives are not meant to take that kind of abuse and will die within months (Voice of experience here). Hitachi makes special 2.5" drives that are meant to be used in server applications like this, look for the 'E' in the part number.

An even better way to see how your laptop uses power in Linux is to run the Intel PowerTop program on it. It will show you what applications and drivers are causing CPU activity. The Fedora developers have clearly been using this tool. My laptop uses LESS THAN HALF of the power at idle than it did just 6 months ago!

By the way, suspend and resume work just great in Linux on my laptop. I had to upgrade the BIOS, though. It suspends when I close the lid, and it resumes when I open it. No muss, no fuss, works every time. It takes a while, but I have a slow disk and lots of RAM. Sometimes the USB drivers get confused after resume, but you just have to reload the kernel modules and all is fine.

If you want better suspend/resume support in Linux, complain to nVidia. They know about their bug but they have not fixed it. When they fix their bug, there will be no more excuses and everyone else's shame will be revealed.

Since someone has brought up PowerTOP and tickless Linux, I should point out http://lesswatts.org .. Using powertop, laptop-mode-tools, and many of the recommendations from that website, I have managed to knock my ThinkPad T60 down to a cool ~13 watt idle.

http://www.lesswatts.org/projects/applications-power-management/race-to-idle.php

Here be hard numbers to back up the "race-to-idle is better" assertion. The basic gist of it (again, with real figures, and not my handwaving) is that the energy used by a busy, but throttled core doing some amount of work in (lets say) 10msec is greater than wide-open core doing the same amount of work in (say) 6msec and then going into a deep sleep for 4msec.

It makes sense to me, many systems run most efficiently at full-throughput; internal combustion engines generally have that property, for example. A throttled core still pays some constant power price for being on *at all*, a sleeping one can literally turn parts of itself completely off.

All that said, I'm sure the best scenario is some combination of dynamic scaling/throttling and sleep states. The only way to verify any optimization technique applies here as well--measure it!!

Gah! Don't let my mom see this article. I want to keep running distributed computing projects! (my CPU is 100% 24/7)

I'll second that opinion about not running your laptop hard drive 24x7. That's just asking for trouble.

Anyone know where can I get one of those Kill-a-Watt gizmos in Canada?

Tim

I gotta say...I've been reading your blog for a little while now. I am absolutely stunned by the incredibly informative articles you write.

This article here has inspired me to post my first comment!

This one in particular is wonderful! I've always been curious about power usage in laptops but never really taken enough interest to investigate. Thank you!

Keep up the awesome articles!

In Australia you can get a noname knock-off of the Kill-A-Watt from Jaycar for about $40, but you may be better off ebay. Search for "Power Monitor Meter" on ebay and you will find them.

I've been playing with mine for a while and it seems to be inaccurate especially at low watts (eg. testing vampire power etc), but accurate enough to get a good idea of which items you should about turning off and which ones don't really matter.

I managed to cut my household electricity usage from about 4kWh a day to about 1kWh, which I was pretty smug about.

lesswatts.org has some more interesting ways of lowering power consumption (at least on Linux). For example, your computers sits polling the CD drives, just in case you happen to put a CD in. You can stop this behaviour, which is slightly inconvenient, but hey we're big boys, we can handle it.

I get about 45 minutes of life on my desktop replacement, so it's pointless to optimize it -- 60 minutes isn't enough to get anything done on a plane anyway. =)

Jeff --

I also own a Dell 300m. What a wonderful machine it was. It has taken a beating, and is now relegated to a completely non mobile linux server. Yes server. The power connections to it have become messed up and I cant unplug it. I still love the thing though. I recently bought an XPS 1530 and aside from the touchpad problems I really like it so far. I bought it shortly after reading up about it and the 1330 here and other places.

Thanks for doing a great job with your blog!

Also noteworthy is that dedicated GPUs, such as the ATI-chip I'm presuming is used in this XPS1330, draw WAY more power than a low-performance chip such as the Intel GMA X3100. So unless you're really going to be playing 3D-games or something on the laptop, an Intel chip is probably a better choice.

ATI drivers have a Optimal Battery life option. I think it almost double my battery time (Idle PC against Idle with Optimal Battery Life in Catalyst Control Center). Very useful indeed. ATI Catalyst Control Center is way better than nVidia Control Panel.

Hey Jeff, speaking in speedstep/Cool'N'Quiet, do they screw up with VMWare Virtual Machines? The program made some bold statments when I turn one VM on about having different clocks. The one thing it did say is that the clock in the VM might be wrong, but that you can sycronize the clock with VMWare Tools. Is there any other problems? Should I turn off speedstep (Always On option in Power Schemes in XP) in my laptop?

For CPU power savings, I recommend RMClock. http://cpu.rightmark.org/products/rmclock.shtml. Good for undervolting and controlling CPU states to much finer detail than you find anywhere else, though it takes a little work to get the hang of it. I have an Toshiba M200 Tablet, and I was able to add a solid 30 minutes to my battery life by tuning the settings.

What we need is a turbo button on laptops. We can set the CPU usage to 25% or 50% then when we need to do something big just press the turbo button and get 100% cpu instead of having to change the settings.

Wow, I never realized there was such a difference in the power consumption of a CPU at idle and maximum power draw.

A comparison between the power consumption of the Dell Inspiron 300M laptop and the the Dell XPS M1330 would have been interesting.

Just so you know, you don't have to manually switch to power savers mode every time you unplug your laptop.

Just click on the battery icon, go to "more power options" and then click on advanced preferences (or something like that, I'm not on my laptop right now). Over there you'll be able to set custom settings on what you want your laptop to do when its plugged into an outlet or on battery power. I've got mine setup to automatically dim the LED and go down to 50% CPU whenever I unplug the power.

You can even change the settings so that actions like closing the laptop lid or pressing the power button do different actions (Shutdown, Hibernate, Sleep, or Nothing) depending on whether you're running off the battery or not.

Best of all, you don't have to fiddle with the settings every time you want to take your laptop with you :D

>>What we need is a turbo button on laptops. We can set the CPU usage
>>to 25% or 50% then when we need to do something big just press the
>>turbo button and get 100% cpu instead of having to change the
>>settings.

It's basically three clicks away:
double-click the battery icon
click "High Performance"

Done

To switch back, double-click the battery icon again and select the previous mode (Balanced or Battery Saver).

My Balanced mode (the mode I always use) is slightly tweaked (to reduce the performance throttles), but for the most part I don't have trouble with my laptop's power use on battery. I guess if my laptop were smaller (ie small enough to actually use on a plane) I'd run into these issues more, but I prefer to use hand-held game systems and books while on the plane, and if I need to make a note for myself or write an email (to send from the airport or hotel), I'll use my phone.

Thanks for the article. I want to use a laptop as a deck with >12 hour battery life, so every watt counts.

I won't need the graphics or networking subsytems on /at all/ though, so I hope I can turn PCI devices completely off.

SSD's should get much more efficient over the coming years.
..but before I go blowing hundreds of dollars on modular bay batteries and SSD's, I'd like to know this:

How exactly did you get per-component wattages? Assumptions? ACPI? I want real time measurement, by component, of power usage of my laptop while on battery.

ethana2@gmail.com

>> BradC, the video will be decoded by the GPU/CPU regardless of the source, computer dvd drives have no decoding capabilities, much less laptop ones.
>> Your best best will always be to rip the dvd to the hard drive.

>A quick search tells me that in the United States, using any software that can bypass the security restrictions of a DVD is illegal, even if you are only using it for personal use.

Bummer.
BradC on April 14, 2008 08:17 AM

While this is technically true, this shouldn't be an issue since they won't know AND further reading of US laws and Fair Use, will show that despite the recently made law(s), the MPAA would have a very difficult time trying to sue due to fair use (in this instance) trumping said laws. While distributing would be very problematical for you if caught, for your own use (when you also own the dvd), well then the MPAA would likely loose outright.

Still, it would be a gamble if you are going to a MPAA conference with your recently ripped dvd files on your laptop... =)

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I just formulated a test of my own to figure out ideal power settings. Record your start time right when you unplug. Use your laptop regularly as you normally would under the Balanced power setting until you hit 50% battery. Record your cpu mem and uptime/current time. Then switch to Power Saver and record what your final stats were when the remainder of the battery drained under the same load. Compare the differences in times between 100-50% and 50-0% Obviously the second time should be longer, but exactly how much longer will tell you if it's worth it. Multiply by 2 then you have a somewhat accurate estimate of what your power needs are and what you stand to gain from using lower power settings.

Surely, your wattage numbers are of the WHOLE laptop, not individual components? Careful when writing "How much power does the hard drive use?", I think what you really meant to say is "How much power does the laptop use when hard drive is a) idle b) defragmenting."

Right?

Because the Core 2 Duo CPU has a TDP of 35 watts (i.e. it consumes 35 watts at most, most if not all of this energy becomes heat, as far as I understand), however it appears you are saying it consumes 63 watts doing to Prime95 torture tests. Something is wrong with those tests, sampling, or with you formulation. Please clarify.

could you please check our internet

Instead of mucking around with power settings on your laptop, why not buy a PC that uses only 8 Watts of power? These little PC's can be mounted on a LCD and run from a solar pack, that would become your 19" laptop...run on free solar :)
You can read more about them and watch a demo at:
aleutia.com/products/demo.html
http://www.aleutia.com/products/demo.html

Bill from Aus'

Great write up.