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Undervolting a Laptop

ScuttleMonkey posted more than 8 years ago | from the too-late-for-my-laptop-graveyard dept.

Portables 262

Delph1 writes "Laptops often comes with two Achilles heels, heat and limited battery time. There are, if not cures, at least remedies to make them less obvious. By lowering the voltage to the processor you can not only drastically lower the heat dissipation, but also increase the battery time significantly. NordicHardware gives a nice walk through on the process and was able to boast 18% lower temperature and a 20% reduced power consumption."

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Underclocking (5, Informative)

selfabuse (681350) | more than 8 years ago | (#14543201)

ATI Tray Tools (or a similar program) will let you underclock your video card too. Good for when you have a hulking gaming laptop, but aren't playing games, and don't want to use it as a space heater for your living room.

What for? (2, Informative)

Poromenos1 (830658) | more than 8 years ago | (#14543343)

I don't think many people have a use for this. The processors shut down when they're not doing intensive work, and when they are (playing games, encoding) you more than likely have them plugged in an outlet. I don't know about heat, as I've never had a problem (I have an Athlon XP mobile).

Re:What for? (0)

Anonymous Coward | more than 8 years ago | (#14543560)

My last 2 laptops (both HPs with ATI video cards- one w/ an Athlon XP, one with a P4) have had serious heat issues. If I leave my keys sitting next to the thing for more then a few minutes, they're nearly too hot to pick up. I guess it could just be me, or just be HPs, since that's what all my experience is with.

Re:What for? (1)

Lehk228 (705449) | more than 8 years ago | (#14543716)

next ime you are looking to buy a laptop try an Acer TravelMate , not the Aspire line Aspires have horrible battery life my travelmate gets at least 3.5hours under average load with wifi enabled, and over 5 hours with wifi off

Re:What for? (3, Interesting)

AngelofDeath-02 (550129) | more than 8 years ago | (#14543705)

He's talking about the videocard in this particular case.

But anyways, you do bring up an interesting point. usual power saving features do things like lower the clock rate when not in use, but lowering the maximum clockrate you would lower the speed of the computer, thus the max power it puts out. Knowing that you will be running the processor at max speed longer, you may or may not gain power/heat savings overall for long complex tasks, but I imagine for simple tasks you would.

now - I don't believe you need to downclock just because you lowered the voltage, but you may introduce system instability ...

That's usually what happens when you overclock without increasing the voltage as well.

BushCo's State Of The Gulags: +1, Informative (-1, Troll)

Anonymous Coward | more than 8 years ago | (#14543437)

Bush states Iran could blackmail the world without, of course, any explanation of the purpose of a blackmail scheme..

Question: What would be the purpose of the blackmail?

Does anyone still believe this sorry excuse for a crock of Shit [whitehouse.org] ?.

Peace is war.
Bad is good.
Disarmament is armament.
Life is death.

Defend America: Arrest, Try, Impeach The White House.

Sincerely,
Kilgore Trout, Super-Patriot

Re:Underclocking (3, Informative)

mjh49746 (807327) | more than 8 years ago | (#14543771)

ClockGen can also be used to undervolt/underclock supported motherboards in desktop systems, too. I routinely use it to save power and lower my temperatures when I'm not doing anything CPU intensive, like Folding@Home.

http://www.cpuid.com/clockgen.php [cpuid.com]

"They are not in Baghdad. They are not in control of any airport. I tell you this. It is all a lie. They lie. It is a hollywood movie. You do not believe them."

I'm glad to see this (0, Offtopic)

eclectro (227083) | more than 8 years ago | (#14543224)


It should also help to save the "special purpose".

Counter productive maybe? (5, Insightful)

squoozer (730327) | more than 8 years ago | (#14543230)

Surely if you drop the voltage your are going to have to under-clock the processor (reasoning that to over-clock you need to increase the voltage). Most processors for laptops already throttle the processor down when under light load now-a-days which must be a great energy saving. Would under volting it really then save more or would you just end up with a laptop that is dog slow? I'm sure if it was this easy one of the big laptop producers would already be doing it as a 20% increase for basically nothing would give them a fantastic advantage.

Re:Counter productive maybe? (1, Insightful)

Anonymous Coward | more than 8 years ago | (#14543313)

There are definite gains to be made, even at the top speed; you just need to experiment. It works quite well because you can specify a voltage for each clock speed (or use the default tables). As long as you don't crash the OS, it won't go any slower than it would have otherwise.

Lots of laptop manufacturers are bundling appropriate software to do this for you these days, too.

Re:Counter productive maybe? (5, Insightful)

NitsujTPU (19263) | more than 8 years ago | (#14543353)

You end up with a laptop that is dog slow. You're right, most modern laptops throttle themselves effectively in order to reduce power consumption.

What the guy is doing, however, is trying to lower the voltage consumption to the line where the processor starts to behave a little flaky, and then pumping it up just a bit over that. Processors are made in big batches, some of them just work better than others. If yours happens to be one of the good ones in the batch, you can reduce the voltage while maintaining performance (not needing to bump down the clock speed).

If you really obsess over it, you go into the research that my roommate does, where he spends endless hours, days, and weeks tweaking processor floor plans and running them through simulators. You might hope to build a more efficient processor through all of this.

I wouldn't recommend doing this if you're not partial to your laptop randomly hanging while you're working on it, but everyone needs a hobby.

Exactly (1)

EVil Lawyer (947367) | more than 8 years ago | (#14543680)

Seriously. I mean, I could pretty drastically "lower the voltage" and "improve batterly life" if I replace the LCD with a single LED, and the hard disk with a block of cheese... but that doesn't quite make it a good idea.

Re:Counter productive maybe? (2, Interesting)

bigtrike (904535) | more than 8 years ago | (#14543398)

Would under volting it really then save more or would you just end up with a laptop that is dog slow?

You might be removing the ability of the system to manage its own power. This was the case with my desktop. Dropping the CPU frequency on my P4 based desktop actually made it consume more electricity. At its factory speeds, the system uses abotu 90W when not doing a whole lot, and about 215W when under heavy load. Dropping the CPU frequency to 300MHz caused it to idle at about 110W usage. I did not experiment with dropping the voltage however, which may have produced a net savings.

Re:Counter productive maybe? (0)

Anonymous Coward | more than 8 years ago | (#14543456)

"Surely if you drop the voltage your are going to have to under-clock the processor (reasoning that to over-clock you need to increase the voltage)."

It's possible. But since the power consumed is proportional to the square of the voltage, you'll see a net decrease in power required per unit computation.

"Would under volting it really then save more...?"

Yes. Power consumption is linear with clock speed. Besides, throttling the processor helps when the processor isn't doing anything. Lowering the voltage helps all the time, so the two could be combined for added effect.

"I'm sure if it was this easy one of the big laptop producers would already be doing it..."

Actually, I think if you look at the core voltages in processors over time, they've decreased, so in a way you're right.

At some point, the transistors won't switch anymore due to the low voltages, but if there's wiggle room to exploit, it's worth looking into at least.

Re:Counter productive maybe? (0)

Anonymous Coward | more than 8 years ago | (#14543574)

Not really. Sure, you WILL come to that point as you lower voltage, but it should be common to get significant undervolts without having to reduce clock speed.

Re:Counter productive maybe? (2, Interesting)

yppiz (574466) | more than 8 years ago | (#14543707)

I underclock and undervolt my laptop using the RightMark CPU utility.

Speedstep can only throttle my processor down to 600MHz (from a max of 1.2GHz) but underclocking reduces it to an effective 300MHz.

I do not notice the performance hit, and I do a lot of photo editing on this machine.

--Pat

Re:Counter productive maybe? (2, Informative)

Marxist Hacker 42 (638312) | more than 8 years ago | (#14543752)

Photo editing, for the most part, is more memory intensive than CPU intensive.

Re:Counter productive maybe? (1)

VlartBlart (948166) | more than 8 years ago | (#14543760)

My two home pc's are both laptops (it's a space thing - even though I have 16 USB devices stuck in one so I may as well not bother) - I can honestly say that they never run "dog slow". You can run Avid on them whilst listening to mp3s, surfing the web and making toast and they don't give a dogs doo-doo.

I think laptops have a bad press as under-powered machines (or dogs) - but they're as good as a decent desktop.

What I'm trying to say (under the influence) is that the power management of a laptop chip does not effect its performance. They can be sprightly little mothers!

Thanks to CPM (Chip Power Management (I made that one up)) - you can drag the uptime up from 24 hours to - oooooh, maybe 36 hrs before it melts down :)

Eh (-1, Flamebait)

Nezzari (927045) | more than 8 years ago | (#14543233)

Why would someone need a longer battery life? Geesh, how much porn do you people watch...

Computer Performance (4, Interesting)

ranton (36917) | more than 8 years ago | (#14543243)

How does reducing the Voltage in this way effect performance? If performance drops, then you could have just bought a computer with less processing power that also had lower power needs in the first place.

If there are no performance problems, then why dont all laptop manufacturers already do this?

--

Re:Computer Performance (4, Informative)

drinkypoo (153816) | more than 8 years ago | (#14543287)

Generally speaking, limiting processor power limits maximum clock rate. If you undervolt you generally underclock. Most mobile processors already have a power-saving scheme that allows you to select the highest speed that will be used while the system is on battery. Even older systems (like my stinkpad A21p with Mobile P3) have multiple speeds and they will run at a slower one automatically when on battery. So there's not much of a difference unless you're reducing voltage to something lower than the system does automatically.

Re:Computer Performance (0)

Anonymous Coward | more than 8 years ago | (#14543354)

it dosent thats the point, cpus are different some can handel undervolting and be stabel some cant.
You se the same syndrome when overcloking some does fine without overvolting others need it to be stabel at higer clockrates.

Re:Computer Performance (0)

Anonymous Coward | more than 8 years ago | (#14543483)

wow SWING and a miss on that one...

more advanced components make better use of the power, in particular this is true with CPU's

so current chips use less power and havebetter batteries, now add the lower power usage by limitingthe voltage and you have even less power usage.

No Con's? (3, Interesting)

randomErr (172078) | more than 8 years ago | (#14543248)

I just scanned through the article and saw they never listed any con's. How much of a performance hit are you taking? Is there any long term damage on the processor or memory? Are you voiding your warranty?

Re:No Con's? (0)

Anonymous Coward | more than 8 years ago | (#14543441)

Well if you look at your machine cross-eyed, it voids the warranty.

So what you do is, add water to the display, turn it on briefly, and claim that it came out of the box that way.

Theres lots of other fun ways to get around warranty requirements

Re:No Con's? (2, Informative)

obious (945774) | more than 8 years ago | (#14543628)

No, no cons. Most processors, especially mobile variants, can operate above their "standard" specification. So even if the spec calls for 2GHz @ 1.5v the processor might be able to operate correctly at 2.3GHz @ 1.5v. Similarly, a processor with a spec of 2GHz @ 1.5v could operate at 2GHz @ 1.3v. Thus, no performance hit. This is because after the processors are manufactured they are tested and separated based on the highest performance they can reach under a set of standards set forth by the manufacture. This means that two processors coming off the same wafer could actually become an AMD 64 2800 and an AMD 64 3000 for example. Now, one of those 2800's could have been a 2950 but since AMD doesn't have a 2950 it was put in the 2800 bin. Think of it as a lowest common denominator that ensures even the shittiest processors run fine. ...and it only voids your warranty if you tell them.

isn't this what speed step did back with the PIII? (3, Interesting)

ulysses38 (309331) | more than 8 years ago | (#14543258)

i'm not so sure about the heat, but it seems that it would follow.

"Mobile Intel® Pentium® III processors with Intel SpeedStep® technology let you customize high performance computing on your mobile PC. When the notebook computer is connected to the AC outlet, the new mobile PC runs the most complex business and Internet applications with speed virtually identical to a desktop system. When powered by a battery, the processor drops to a lower frequency (by changing the bus ratios) and voltage, conserving battery life while maintaining a high level of performance. Manual override lets you boost the frequency back to the high frequency when on battery, allowing you to customize performance.?

Re:isn't this what speed step did back with the PI (2, Interesting)

krgallagher (743575) | more than 8 years ago | (#14543637)

"isn't this what speed step did back with the PIII"

This is what AMD did with their PowerNow!(TM) [amd.com] technology. It dynamically adjusts CPU power consumption based on CPU load. According to AMD, it can reduce CPU power at Idle by 75%. I know on my laptop, I can hear the fan speed up and slow down based on the load on the CPU.

lol (3, Informative)

Anonymous Coward | more than 8 years ago | (#14543276)

OR you can just buy a laptop that allows you to do this stuff natively.

I have an acer aspire 1691 laptop and i can control how fast i want the cpu to run ,how bright the panel is if wifi is on and stuff like that all through software.

Why would I undervolt it when my laptop can do it through software already.

Re:lol (1)

Da Zeg (946564) | more than 8 years ago | (#14543455)

I have an acer aspire 5021 (ML-28) and the lowest voltage the amd drivers will go to is 1.0 and 1.5 respectivley with no steps between 100% and 50% cpu clock through CPUID i run at the lower speed at 0.925V and the highter at 1.325V with no hitches apart from everything runs cooler and longer. I also get the added bonus of being able to set speeds in between.

Bad Idea (2, Informative)

AKAImBatman (238306) | more than 8 years ago | (#14543283)

This sounds like a really BAD idea to me. Low Voltages can produce the exact opposite of the intended effect. Instead of lowering the power consumption, you'll get higher amperage spikes as the equipment draws more power to compensate. The result is that you could be damaging your electronics and not even know it.

I'll grant that modern manufacturing methods have greatly increased the survivability of hardware under less than ideal conditions. However, that shouldn't be taken to mean that you can't do serious hardware damage by operating outside of the device's specifications.

Parent is a Bad Idea (3, Interesting)

Anonymous Coward | more than 8 years ago | (#14543329)

Whee... I mean, CMOS logic will never "try to compensate". There is no feedback. In a typical digital system, only switching power supplies will draw more current when their *input* voltage drops. However, Vcore is the *output* voltage of those, not input.

Re:Parent is a Bad Idea (0)

Anonymous Coward | more than 8 years ago | (#14543513)

when's the last time you took and ee course, the 70's?

Re:Parent is a Bad Idea (2, Informative)

StikyPad (445176) | more than 8 years ago | (#14543773)

TTL is not a current-intensive design. There is some amount of current, but the only reason your CPU draws a significant amount of power (current x voltage) is because there are millions of transistors. The transistors will not draw more current to compensate unless there's a current feedback loop (there isn't, otherwise you wouldn't need, or even be able to have, external voltage controls); they'll simply cease to function properly. There is a feedback loop for the power supply on the motherboard (just a regulator really), but that's what we're manipulating, so overcurrent issues shouldn't exist. More importantly, the regulators on the motherboard should prevent overcurrent conditions.

The designs are trade secrets, so we'll probably never know for sure, but it doesn't even make sense to put any sort of voltage/current regulation on the chip itself since a) real-estate is at a premium b) regulators need to be relatively large, since they handle ALL the current for the CPU and c) they generate a LOT of heat. I haven't looked at laptop motherboards, but on a desktop motherboard, you'll see usually 3-6 transistors mounted vertically screwed to heat sinks near where the power supply connects. Touch them if you want. The heat sinks should be grounded, so the only thing you'll probably hurt is your fingers.

Re:Bad Idea (1)

JumboMessiah (316083) | more than 8 years ago | (#14543584)

Not necessarily true in open loop systems. Amperage draw is heavily influenced by the voltage applied to the device. Though there are other factors involved (aka clock speed), a lower input voltage will almost always result in a lower amperage draw, which results in lower power consumption.

I've never seen a light bulb stay the same brightness when I reduced the voltage to it. It gets dim, draws less amperage, and less power.

Ohms Law [wikipedia.org] regulates this, though in AC environments it isn't as cut and dry as V = I * R.

Re:Bad Idea (5, Informative)

serbanp (139486) | more than 8 years ago | (#14543608)

Instead of lowering the power consumption, you'll get higher amperage spikes as the equipment draws more power to compensate.

Sorry, this is wrong in the context of a CPU power supply.

When you lower the core voltage, several things happen at once:

1) the power dissipation due to the clock switching is lowered with the square of the voltage reduction. i.e. a reduction from 1.3V down to 1.1V will reduce this power component by 40%

2) the power dissipation due to the junction leakage and off-state punchthrough decreases by the ratio of the voltage.

3) but the switching speed of the MOSFET transistors decreases. Effects 1 and 2 are good as they mean an overall lower power dissipation. For 90nm processes and up, effect #1 dominates. For 65nm and below, the effect #2 becomes increasingly larger.

The downside is #3. Lowering the voltage means that some critical paths inside the CPU logic could become longer than the clock period, generating timing violations and system crashes. The only remedy against this is under-clocking.

In the end, the one thing you can gain by under-volting is the margin between your particular CPU and the lousiest one in the same class that will still perform OK at the same clock speed. As each CPU is tested and binned especially for power dissipation AND maximum clock speed, this margin is low and the gains minimal. And you spend a lot of time to find out what is the lowest safe voltage.

If you want less power dissipation and longer battery life, under-voltage and under-clock. This is done automatically already in the mobile CPUs, both from Intel and from AMD.

Re:Bad Idea (2, Informative)

serbanp (139486) | more than 8 years ago | (#14543725)

Ooops, got carried away and did not really refute the dumb claims the OP made. Yes, the CPU is a monotonic load (i.e. when the voltage decreases, the current decreases).

The OP may have had in mind some constant-power type of load, where the current consumption is (indirectly) driven so that the output power stays the same. From the I-V perspective, the CPU is a glorified non-linear resistor.

Re:Bad Idea (0)

Anonymous Coward | more than 8 years ago | (#14543668)

Boy do you have it ass-backwards. Given a resistance and discharged capacitance (of course in series), a higher voltage applied actually causes more instantaneous current to flow to the capacitor. A lower voltage causes less instantaneous current to flow to the capacitor.

Since all wires on chips are basically resistances and capacitances, I'll leave the conclusion about which causes greated current "spikes" as an exercise for the reader.

Now how about the transistors? Same deal. Lower voltage means lower short circuit current. Total power depends on the switching time.

Anyway, device specifications typically do have low voltage modes. There's a nice graph that can be drawn to compare voltage versus frequency that shows what combinations are possible.

This argument is again independent of transistors designed specifically for high voltage or low voltage. Just a generalization for wires and CMOS.

Been doing this for almost a year with CHC (2, Informative)

Anonymous Coward | more than 8 years ago | (#14543297)

CHC = Centrino Hardware Control, now called Notebook Hardware Control [pbus-167.com] .

CHC/NHC even has built-in stability testing.

It's fairly easy to run 400MHz FSB Dothan CPUs at 533MHz FSB on Sonoma (i915) or ATI Xpress200 laptops. I run a Pentium-M 715A (1.5GHz) at 2GHz with only 1.14v.

Re:Been doing this for almost a year with CHC (1)

evalf (931500) | more than 8 years ago | (#14543787)

A big advantage Notebook Hardware Control (NHC) has over the RMClock utility is that it does not override the power scheme setting that are applied by the computer's manufacturer's software: for example, using NHC I can define the different voltages applied for every multiplier, but still use the IBM utility that came with my thinkpad to choose whether I want the lowest/highest/whatever multiplier, whereas the RMclock utility takes control over everything.

Another thing to take into account is that NHC has many more functions, such as temperature monitoring, GPU undervolting, HDD SMART monitoring, and so on...

I also read somewhere (do not remember where, and I did not bother comparing myself), that the CPU occupation was lower with NHC than it is with RMClock (even though it has more functionalities).

laptops already have step by step instructions (4, Informative)

method77 (943066) | more than 8 years ago | (#14543303)

at least my Thinkpad does. The 'access IBM' button explains everything for you or right-clicking on the taskbar battery icon gives you choices of battery saving which does everything mentioned in the article. I am not advertising IBM or anything. Only pointing that out. I am sure other brands have similar functions too.

Optimization... for human usability (1)

rsborg (111459) | more than 8 years ago | (#14543307)

This writeup is great. I just bought a cheapo laptop (Turion ML-32) and other than increasing RAM to 1GB and getting a faster (and cooler/more efficient) 5400RPM laptop HD, I think that reducing power output is one of the most important things for usability.

Other than just battery life, a reduced heat profile will move the laptop from a desktop replacement to a more usable all-around better box. Will still pale in comparison to my wife's powerbook, but hey, this was half the price and I still can't use OSX at the office (damn intranet IE only webapps).

What's New? (1, Interesting)

Anonymous Coward | more than 8 years ago | (#14543315)

My six year old Dell Latitude has bios settings that automagically step down the cpu voltage when the laptop is unplugged. What's new about this?

Good luck... (1)

XflopThreeShitty (943599) | more than 8 years ago | (#14543317)

...playing Quake 4 with that slower laptop though. But for word or other simple tasks - fine.

I'm not sure which is more surprising (2, Interesting)

Marxist Hacker 42 (638312) | more than 8 years ago | (#14543337)

That the CPU can run at a lower voltage- or that voltage of the CPU on a modern motherboard is SOFTWARE Selectable.

Re:I'm not sure which is more surprising (1)

evilviper (135110) | more than 8 years ago | (#14543803)

That the CPU can run at a lower voltage-

Not surprising at all. It's a mainstay of the processor industry. Since the start of the PC, processor voltage has been decreasing every generation. Generally, the only difference between AMD's "desktop" CPU and their "mobile" CPUs is the stringency of the testing. A mobile CPU that can't handle extreme underclocking/overclocking gets labled as a desktop chip.

or that voltage of the CPU on a modern motherboard is SOFTWARE Selectable.

Everything you can set in the BIOS is software selectable. I can understand the concern, but all CPUs have built-in safety circuitry that should allow them to automatically shut-down and prevent damage.

18% -- that's really funny (5, Insightful)

Jason1729 (561790) | more than 8 years ago | (#14543339)

How do they come off saying a reduction from 78 to 64 degrees F is an 18% reduction in temperature? The Fehrenheit scale is arbitrary and does not have a meaningful zero point.

In celsius, their reduction is 26 to 18 degrees, a reduction of 31%

Why not define a new scale with the same degrees but 0 degrees (new scales) = 63 degrees F. Now on the new scale they've reduced the temperature from 15 to 1 degree, a reduction of 94%....wow that's way better than their lousy 18%.

Their number is totally meaningless.

Also, "undervolting" is not a word.

Re:18% -- that's really funny (0)

Anonymous Coward | more than 8 years ago | (#14543404)

No, what they meant was that the temperature now is -25 F. This laptop can also work as a refrigerator. Don't ask the physics behind it, because it doesn't apply to computers. We are now in the information age, right? Obviously they are just hacking the Matrix control computers.

Re:18% -- that's really funny (2, Informative)

Da Zeg (946564) | more than 8 years ago | (#14543412)

We already have the kelvin scale where 0 is absolute zero - where all particles in a mass would have no energy. 0 K = -273 C All calculations involving heat and energy should be done using this scale or become invalid And I really doubt that the kelvin scale was used to give the figures quoted in the first post. They seem a bit high and arbitrary.

Re:18% -- that's really funny (1)

Politburo (640618) | more than 8 years ago | (#14543678)

All calculations involving heat and energy should be done using this scale or become invalid

Please don't forget Rankine [wikipedia.org] .

Re:18% -- that's really funny (1)

mattcoz (856085) | more than 8 years ago | (#14543474)

You make the same mistake by using Celsius, it's zero point is only meaningful for water. The only truly meaningful zero point is absolute zero. So if you convert the temperatures to Kelvin you'll see that it was a 2.6% decrease.

Re:18% -- that's really funny (0)

Forbman (794277) | more than 8 years ago | (#14543478)

The Fehrenheit scale is arbitrary and does not have a meaningful zero point.

Umm...*every* temperature scale (just like linear measurements) are arbitrary.

It just so happens that Kelvin coincides nicely with an unobtainable measuring point. You could just as easily factor a thermal scale that rises at 0.857347235 the "rate" of the Kelvin scale. Say, in the Stupid thermal scale, boiling water is at 5.2 deg Stupid, instead of 212 deg F, 100 deg Cel, or 373 deg Kelvin.

The *advantages* for one system or another are not always so apparant. Is it better to calculate trig-related math in degrees, gradients or radians? For trivial things, radians is a whole heck of a lot easier than degrees. Is it better to do geometrical maths in cartesian coordinates, or use some other coordinate system?

In the end, one system vs another explain the same thing correctly and to the same degree of "accuracy".

Re:18% -- that's really funny (1)

Mr. Underbridge (666784) | more than 8 years ago | (#14543578)

It just so happens that Kelvin coincides nicely with an unobtainable measuring point.

No, it's actually much more fundamental than that. Essentially, it's the point at which a given substance has zero internal energy - which is to say, a temperature of 0. It's not a coincidence - absolute zero is the point at which a given substance literally has no temperature as we know it. I can't think of a more appropriate zero point for a scale.

Re:18% -- that's really funny (1)

santiago (42242) | more than 8 years ago | (#14543647)

Say, in the Stupid thermal scale, boiling water is at 5.2 deg Stupid, instead of 212 deg F, 100 deg Cel, or 373 deg Kelvin.


Just to nitpick, there's no such thing as "degrees Kelvin". It's just "Kelvins". e.g. "Water boils at 373 Kelvins."

Re:18% -- that's really funny (3, Informative)

Formica (775485) | more than 8 years ago | (#14543492)

The Celsius zero is just as arbitrary as the Fahrenheit zero. The only true "zero" is absolute zero, at -273C or -459F. Using either scale, the "percentage reduction" is around 2.7%, for what it's worth. It shouldn't matter what scale you use when talking about percentages, assuming you use the true zero. If an object becomes 10% lighter, it doesn't matter whether you use pounds or kilograms, does it? Of course, you use percentages even if it doesn't make sense. (78-64)/78 is around "18%", but isn't a very meaningful number. Switching to Celsius doesn't help here, but Kelvin (or Rankine for those Fahrenheit fans) does.

Re:18% -- that's really funny (3, Insightful)

jandrese (485) | more than 8 years ago | (#14543621)

Wouldn't it make more sense to compare the percentage drop against room temperature. As in:

Pre: 24 degrees Fahrenheit over room temp
Post: 12 degress Fahrenheit over room temp, a 50% savings!

Obviously no amount of undervolting would ever get the processor to absolute zero, it's going to bottom out at room temperature (when reduced to 0 volts).

Re:18% -- that's really funny (0)

Anonymous Coward | more than 8 years ago | (#14543498)

Why not define a new scale with the same degrees but 0 degrees (new scales) = 63 degrees F


Why not just throw out that pesky third "law" of thermodynamics [I never liked it, anyway], and define the zero point as 64 F? Wouldn't that give you a 100% reduction, using your calculations?

Re:18% -- that's really funny (1)

shawn(at)fsu (447153) | more than 8 years ago | (#14543511)

I didn't know that temperature needed a "meaningful zero point" to be useful? How do you determine a "meaningful zero point" anyway. As long as long as you state the scale used what's the problem?

Re:18% -- that's really funny (1)

boldtbanan (905468) | more than 8 years ago | (#14543592)

My 0 degrees as 64 degrees, so my temperature reduction is (14/0)% = (infinity)%. I win. :)

Re:18% -- that's really funny (0)

Anonymous Coward | more than 8 years ago | (#14543667)

At least do your math right. It'd be

((14 - 0)/14) * 100% = 100%

Re:18% -- that's really funny (0)

Anonymous Coward | more than 8 years ago | (#14543709)

You do not win. You should have failed 1st year calculus. Division by zero does not equal infinity.

Re:18% -- that's really funny (1)

cosmicdog (948633) | more than 8 years ago | (#14543593)

Their number is not 'totally' meaningless. It's just not totally meaningful. I'm an American and Fehrenheit makes sense to me. If the article was addressed to a group of Physics students, I'm sure that they would have used more absolute, concrete numbers. Now, Kelvin would not be very useful for the average folk because of it's low 0 point. Temperature changes that humans can experience and tolerate would barely register as a change on that scale. That's just my opinion. As far as the term 'undervolting', it is a word. People coin words and phrases all the time. Underclocking is not in Webster's Dictionary, but is has meaning. The same thing with Undervolting. It has meaning and is distinct from the meaning of any other word in the language. It's a word, they made it up. (or someone did).

Re:18% -- that's really funny (1)

teslar (706653) | more than 8 years ago | (#14543767)

Now, Kelvin would not be very useful for the average folk because of it's low 0 point. Temperature changes that humans can experience and tolerate would barely register as a change on that scale. That's just my opinion.

Wrong.
Kelvin is exactly the same scale as degrees Celsius. The difference between the two is simply that the zero point offset by 273.15 units. So any change would register exactly the same on scales in either degrees Celsius or Kelvin, the numbers would just be higher in Kelvin.

Perhaps you were referring to the fact that relative increases may appear smaller. But as the parent already pointed out, looking at % increases in this way is completely meaningless.

If it is 0 degrees Celsius today, and tomorrow will be twice as cold, what will the temperature be tomorrow?

Re:18% -- that's really funny (5, Insightful)

santiago (42242) | more than 8 years ago | (#14543673)

The correct zero point to determine the reduction in heat output would be room temperature. Compare the difference between room temperature and the high-volt processor with the difference between room temperature and the low volt-processor. After all, if it were outputting no heat at all, it would be sitting at room temperature, a 100% reduction in heat output from its initial running state.

Re:18% -- that's really funny (1)

Glonoinha (587375) | more than 8 years ago | (#14543697)

I agree with you, but here's one thought : take the temperature at which your machine quits working (overheats) as a baseline - if they have increased the distance from that temperature (downward) by a certain thermal range - that delta would be the same measured in any current normal scale (Celcius, Farenheit, Kelvin.)

I'm guessing, but something tells me that 18% isn't going to be that delta.

Well, it can be done...... (1)

AKosygin (521640) | more than 8 years ago | (#14543730)

If they simply converted to Kelvins before doing the percentage..... but then, were they smart enough to use how many Kelvins?

Re:18% -- that's really funny (1)

Martin Blank (154261) | more than 8 years ago | (#14543746)

If you want to be pedantic, the percent reduction in temperature was:

25.6C = 298.8 K
17.8C = 291.0 K

(291.0 K / 298.8 K) = 0.974

That makes it a drop of about 2.6%, not 14% or 31%. Doesn't sound nearly as impressive, but it is more accurate.

Temperature Discussion (1)

JoeGugel (948650) | more than 8 years ago | (#14543750)

There is little arguement to be made based on what temperature scale is used. Every temperature on any scale has a 1:1 equivalent on another scale.

The proper means to calculate a percent change in temperature would be to divide the change in operating temperature by the difference between the normal operating temperature and the inactive temperature. The inactive (no power) temperature is the "meaningful" constant everyone seems to be complaining about. "Zero" means little here.

([normal operating temp] - [new operating temp]) / ([normal operating temp] - [offline temp])

What scale you use for the temperatures is completely irrelevant because they divide out.

Re:18% -- that's really funny (1)

HermanAB (661181) | more than 8 years ago | (#14543762)

Well, I suppose undervolting is revolting...

Re:18% -- that's really funny (1)

tedgyz (515156) | more than 8 years ago | (#14543774)

Mod parent overrated.

That's not insightful. Their knowledge of math is sketchy at best.

RESULTS ARE IN CELCIUS (0)

Anonymous Coward | more than 8 years ago | (#14543805)

Look at the image
http://www.nordichardware.com/skrivelser_img/465/t empgraf.gif [nordichardware.com]

See the big "C" at the end of the scale?

That is REALLY hot!.

But yes, the percentage is meaningless. They should have at least subracted out the ambient temperature which should have been 25-27 C giving a decrease in *temperature* of 26-27%

Further work would need to be done to determine the reduction in *thermal engergy* output in watts or BTUs.

Why? (2, Insightful)

Eightyford (893696) | more than 8 years ago | (#14543351)

Why not just underclock the processor? Adding more ram, dimming the screen, and using a virtual cd drive should also help considerbly.

I modded my Dual-Heel Processor (5, Funny)

digitaldc (879047) | more than 8 years ago | (#14543371)

Laptops often comes with two Achilles heels, heat and limited battery time.

You know, I just found about this and I have modded my Laptop to the EXTREME!
I just went on a website and then tinkered with my new Dual-Heel Processor.
It's so EXTREME the battery catches fire 10 seconds after it finishes booting up.

It's 18% cooler only in Celsius (0, Redundant)

RNLockwood (224353) | more than 8 years ago | (#14543375)

If you use the American temperature scale (degrees Farenheit) you get a smaller temperature drop: 15%. If you measure in Kelvins you only get 4%.

For an excercise devise a scale that will give a 50% temperature drop, it's a lot more impressive and means about as much as measured in Celsius!

Re:It's 18% cooler only in Celsius (3, Funny)

pierreTheBear (948643) | more than 8 years ago | (#14543615)

Ok, so my iMac G5 is running at about 50 deg C. That's 323 degrees Kelvin (ie, total thermal energy above absolute zero).

An 18% reduction in absolute temperature would reduce my processor to 264 deg K... that's equal to -9.15 degrees Celsius.

My kitchen freezer can't even get that cold! If I undervolted my iMac, I could be chillin' my b33r right now as well!

Too much misinformation here. (4, Interesting)

TheGuano (851573) | more than 8 years ago | (#14543388)

Some facts:

Undervolting is NOT underclocking. You run the same clock speed, you just provide the CPU with less juice.

You do NOT need to underclock to undervolt, though if you're trying to hit a super-low voltage, a lower clockspeed will let you do it.

It can be perfectly safe. If you undervolt, and successfully run a Prime95 torture test for 24 hours, you're pretty much set. I'm currently running a 1.8Ghz Dothan Thinkpad at 1.134V (default at 1.8 is 1.340), and 0.700v at 600Mhz (default is 0.980 volts). That's on par or lower than those 1.0Ghz ULV Pentium-Ms!

Re:Too much misinformation here. (2, Insightful)

TheGuano (851573) | more than 8 years ago | (#14543418)

Oh, one more thing: undervolting is generally SAFER than overclocking, or overvolting to overclock. Providing less power to the CPU can cause errors or crashes, but it won't fry your CPU like overclocking/overvolting will!

Lowering the voltage does not affect performance (2, Interesting)

sammydee (930754) | more than 8 years ago | (#14543391)

Lowering the voltage REDUCES current flow through the chip, reducing power consumption and heat output. The downside is, you can only lower the voltage to a certain limit before it goes below the threshold switching value for the transistors and the processor stops working. This causes no permanent damage, and is totally reversible by raising the voltage again. The lower the clock speed, the lower the voltage can be pushed. It is common practice among overclockers to try and push the voltage as low as possible for a given clock speed to reduce heat output.

I do this too. (5, Funny)

Anonymous Coward | more than 8 years ago | (#14543396)

I find that if you disconnect the battery entirely, you end with 0 voltage draw on the battery. 0 amps are drawn, too. You can then go for many days without having to recharge the battery! This greatly increases overall battery life as well because of less wear and tear. With my Windows desktop environment being riddled with spyware and viruses, my productivity is only reduced slightly when I do this.

Re:I do this too. (1)

pscottdv (676889) | more than 8 years ago | (#14543781)

And you get a whopping 68% lower temperature!

Nothing new for now... (5, Informative)

Razlor (846966) | more than 8 years ago | (#14543416)

This procedure was described some months ago here [notebookforums.com] , but without obnoxious "i spread my article over infinite pages in order to get more clicks" practice. I have been undervolting my Dothan a long time, using this [localhost.ruhr.de] little patch and some modifications to vidc. This keeps the fan off most of the time, saves some battery life and has no other impact whatsoever.

Undervolting? (0)

Anonymous Coward | more than 8 years ago | (#14543417)

I'd comment on that malapropism, but I'm in an underwording mood today.

Undervolting is not underclocking. (4, Informative)

Destoo (530123) | more than 8 years ago | (#14543433)

It seems a lot of people just assume that undervolting would be something akin to getting the inverse result of overclocking.

Here's the link to an interesting page about undervolting pentium M processors [thinkwiki.org] .

Experience shows that the processor may continue working correctly at lower-than-nominal voltages and frequencies, thereby reducing power consumption, heat and fan noise.

Even if your system seems stable, it may still suffer transient faults leading to arbitrary data corruption. In addition, errors in following these instructions (or changes between processor models) may operate the CPU above its nominal parameters, with effects up to and including laptop meltdown.

There's also a thourough discussion and user results from undervoltage on this thread [anandtech.com] .

Re:Undervolting is not underclocking. (1)

rjstanford (69735) | more than 8 years ago | (#14543785)

Even if your system seems stable, it may still suffer transient faults leading to arbitrary data corruption. In addition, errors in following these instructions (or changes between processor models) may operate the CPU above its nominal parameters, with effects up to and including laptop meltdown.

Other than that, Mrs. Lincoln, how was the play?

There is no performance difference (2, Informative)

Anonymous Coward | more than 8 years ago | (#14543467)

Undervolting a processor without changing the clock does not affect performance. With a processor, the clock synchronizes the electric pulses which maintains a constant instructions-per-cycle rate. As long as the voltage is high enough to create adequate digital voltage differences, the processor will function properly. You're basically using a letter opener instead of a kitchen knife to open a sealed envelope. Both approaches get the job done, but one's more efficient than the other. And if asked to do so, you could open the same number of letters per hour with either tool.

Also, for the Gentoo users: HOWTO Undervolt a Pentium M CPU [gentoo-wiki.com] .

mnemonic_

NordicHardware (-1, Flamebait)

Anonymous Coward | more than 8 years ago | (#14543468)

Hardware for the Aryan Master Race.

Re:NordicHardware (-1, Flamebait)

Anonymous Coward | more than 8 years ago | (#14543723)

Aryan Nerds represent.
http://www.nazi.org/ [nazi.org]

been doing this for years (1)

diitante (779203) | more than 8 years ago | (#14543509)

intel w/ speedstep and "powernowd" (in linux) support. my 1.6Ghz PM runs at 600-800Mhz 90% of the time. significantly lower heat

Undervolting is NOT the solution (0, Interesting)

Anonymous Coward | more than 8 years ago | (#14543526)

This sounds good but because of Ohm's Law where the volts(EMF) times amps(current) equals watts the device will demand so many watts to operate and if device doesn't have enough voltage it takes it from current. This increase in current will increase temperature since the circuits are designed for so much current and increasing the current will just produce heat. Also you can screw up the voltage reference for the digital signal since the each 1 needs so many volts for the circuit to know it is really 1 and 0 is really 0.
Most circuits in laptops are desgined to their limits of design and manufacturing production so I personally won't screw this up. Desktop or workstations have an little more leeway on design so I would play this theory on those first.

Re:Undervolting is NOT the solution (1, Informative)

Anonymous Coward | more than 8 years ago | (#14543555)

Ohms Law doesn't work like that..

If you lower the voltage, the components will simply stop working as you go below their operational rate.

Put it another way.. as you approach zero volts, does current approach infinity? The answer is no.

Re:Undervolting is NOT the solution (3, Interesting)

onkelonkel (560274) | more than 8 years ago | (#14543747)

Say What?? Either you are trolling or you fundamentally misunderstand Ohm's law.

Resistive loads (which, to a first approximation, a CPU is), don't "demand...Watts", they "draw current". The load resistance doesn't change, so Ohm's Law I=V/R says that if you drop the voltage, the current decreases. Drop the voltage 5%, you DECREASE current 5%. Your total power (V * I) is now decreased by 10%.

As for "screw up the reference voltage", this is and remains system ground, or 0 V. Yes, at some lowered voltage, the CPU will cease to operate. Assuming the CPU still runs, a logic level of 2.85 V is just as good as 3.0 V.

dual boot? (1)

DarkClown (7673) | more than 8 years ago | (#14543545)

So looking at this I can't tell what happens in a dual boot situation - it describes setting up 'autostart' - does this happen at the os level?
What i'm wondering is, since this things looks like a windows utility, will the changes stay in effect when I boot into linux? Is there a linux solution if not?

Non-expert wants to try it! (1)

erroneus (253617) | more than 8 years ago | (#14543550)

I would love to see if I could make my laptop a little less warm, so let's see if anyone can help:

I am running the following:

Dell Inspiron 8600, 1.6GHz, 768MB RAM, ATI Radeon 9600. Running Fedora Core 4 fully up to date and using proprietary drivers successfully.

The cpuspeed daemon seems to be doing it's thing properly by adjusting stuff on the fly so I suspect it is in /etc/cpuspeed.conf that I can effectively make adjustments but I don't know where to begin tweaking. So, anyone out there already know what I should do to give this a try?

No performance loss (3, Informative)

Delph1 (936230) | more than 8 years ago | (#14543603)

There is no performance hit here. The thing with undervolting is trying to find the sweetspot for the processor. I.e. the lowest possible voltage at which the processor works just as it is suppose to. If you are experiencing problems you've gone too far. Some users have managed to go as far as 30% with their Pentium Ms.

USB often has its corners cut... (3, Interesting)

PHanT0 (148738) | more than 8 years ago | (#14543618)

I work in support at a hardware company which sells some USB products. On a related note to this article, the processor isn't always the one whose voltage is dropped. When one of customers call-up using a laptop, more often then not the device is fine and it's the laptop who is underpowering the USB port in order to save battery life which is causing the problem.

Just food for thought.

Done something like that (1)

jigjigga (903943) | more than 8 years ago | (#14543633)

I run my 2ghz pentium m at 200mhz in the car to play mp3's. I get around 5 hours of constant playback with it downclocked to that level.

Re:Done something like that (1)

rjstanford (69735) | more than 8 years ago | (#14543807)

Wow. That's almost as long as a laptop with a new battery running at a pretty high speed. Of course, you can also spend $50 or so (probably not a big deal if you've got a 2ghz M laptop) and get a mobile laptop power supply like one of the Targus ones... then it will last (effectively) forever.

Transmeta's LongRun technology (3, Informative)

yorktown (947019) | more than 8 years ago | (#14543645)

Back in 2000, Transmeta started producing chips with Longrun [transmeta.com] technology, which automatically varied processor frequency and voltage many times a second in response to the current processor load. The technique is quite effective in reducing heat and increasing battery life.

Re:Transmeta's LongRun technology (0)

Anonymous Coward | more than 8 years ago | (#14543801)

Hate to break it to you but every mobile CPU has been doing this for many years.

Sacraficing speed for power? (2, Interesting)

Dream1979 (946688) | more than 8 years ago | (#14543779)

By lowering the voltage to the processor you can not only drastically lower the heat dissipation, but also increase the battery time significantly. But wouldn't that significantly reduce the speed of the processor? If so it will take longer to perform the tasks, and that pretty much cancels out the longer battery life... No?
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