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Intel SpeedStep, Windows XP, and confusing Power Profiles

Posted 29 September, 2007 at 8:25pm by Michael Chu
(Filed under: Personal Computers)

This information is elsewhere on the net, but not necessarily easy to find, so I'm "re-documenting" it here while I still remember it from my work in this area back in 2002-2005. These states are mapped for Windows XP terminology only, but a great deal of IT machines are still out there that use XP so it's probably still relevant for another year or so. The impetus to write this down was due to my wife's work laptop "being loud all the time". I took a look and discovered that it was her fan that she was complaining about. Since it had the Centrino Mobile Technology sticker, I knew the processor had to be Pentium M or later, fully supporting Intel Enhanced SpeedStep Technology, so I changed the power profile to allow the CPU to enter a low power state while the laptop was plugged in (which is almost all the time). About ten minutes later, everything was perfectly quiet (the fan having stopped running for the first time).

Brief Background
Because battery life was becoming a bigger and bigger concern on laptop and notebook computers, Intel introduced Intel SpeedStep Technology to their mobile processors that allowed the clock frequency (how fast the processor ran) to be reduced. The original processors would switch to a low frequency (or performance) mode when the laptop was unplugged and running on batteries. The slower frequency used less electrical power and, therefore, battery life could be increased. Later Enhanced SpeedStep Technology was introduced that could switch between a low frequency and high frequency state as needed by the application - if it was a low demand application (like reading a Word document) then the processor could remain in low performance mode, but jump up to high performance when you briefly ran your Excel calculations. In this mode, the processors mostly stayed in low performance mode (due to how people use computers - bursts of activity that take a small amount of time separated by long periods where the user is just reading or thinking) and jumped up for a few seconds at a time to a high performance mode. This way, you almost got the same battery life as being in low performance the whole time, but had almost the same responsiveness and performance of a system running all the time in high performance mode. Later, with the release of Pentium M (the first processor sold as part of Intel Centrino Mobile Technology launched in March 2003), support for multiple frequencies (not just a high and low performance, but points in between) was added to further fine tune this feature.

The problem is, even if you understand your computer did all of this, how do you make sure the technology is on? With Windows XP, the settings are hidden and implied by specific power schemes.

Windows XP Power Schemes
In Windows XP, you can access the power profiles by going to Control Panel -> Power Options -> Power Schemes. There are a number of Windows XP built-in power schemes (I guess they're called power schemes - not profiles… I'll use power schemes from now) that I'll list below in table form. Each power scheme has a group of settings for when you are Plugged In and Running on Batteries with respect to monitor turn off, hard disk turn off, standby, and hibernation. From this user interface, it's easy to assume that's the only difference between each of the power schemes, but in truth there are hidden meanings to each setting when it comes to how the processor is programmed to react to different loads (computing tasks). Here's how it boils down:

Built-In Scheme Plugged in behavior On battery behavior
Home/Office Desk CPU(s) run in highest performance state CPU(s) intelligently select a performance state based on demand
Portable/Laptop CPU(s) intelligently select a performance state based on demand CPU(s) intelligently select a performance state based on demand
Presentation CPU(s) intelligently select a performance state based on demand CPU(s) begin in lowest performance state and then get slower and slower via software manipulation
Always On CPU(s) run in highest performance state CPU(s) run in highest performance state
Minimal Power Management CPU(s) intelligently select a performance state based on demand CPU(s) intelligently select a performance state based on demand
Max Battery CPU(s) intelligently select a performance state based on demand CPU(s) begin in lowest performance state and then get slower and slower via software manipulation

Now, looking at this table, one could assume that "Minimal Power Management" & "Portable/Laptop" and "Presentation" & "Max Battery" are redundant. From a processor point of view, each pair is exactly the same, but the options for hard drive turn off, monitor turn off, and stand by differ. It's also interesting to note that there's no way (by choosing one of these schemes) to simply put the processor in its low performance state without it getting slower and slower. Having worked with battery life on notebooks with Centrino Mobile Technology for three years of my time at Intel, it still irks me that people (like Microsoft) don't think we (as in Intel - I know I left almost two years ago, but after almost seven years of being indoctrinated to think like an Intel corporate citizen, the "we" is hard to avoid) know what we're doing. In any case, there is ample evidence that if you're using your machine for business activities (that pretty much includes most people - the big exceptions being gamers and 3D modelers), then you want the processor driver to intelligently use Intel SpeedStep to control your processor speed. The power advantage of running at low performance (and having the OS additionally throttle the performance by halting the clock more and more) doesn't really by you that much more battery life. So, I usually recommend everyone to just switch to "Portable/Laptop" and alter the power down times to their own personal liking.

If you have other power schemes listed, then these were made by someone other than the Microsoft Windows XP installation. For example, my Dell Inspiron comes with four more settings called: Maximum Battery (QuickSet), Maximum Performance (QuickSet), Presentation (QuickSet), and Custom Setting (QuickSet) - none of which tell me what mode the processor will be operating in. You can also make your own power scheme by using the "Save As…" button - the processor mode will be determined by the power scheme you started with. For example, if you changed the settings of "Portable/Laptop" and then hit "Save As…" to make your own scheme, then your scheme will also have the processors changing their performance levels to match the tasks you're running on your computer.

There is a command line tool that lets you find out (and even alter) the performance mode of your CPU(s) as related to each power scheme. POWERCFG.EXE allows you to look up specific power scheme settings and change them from the command line. It actually does a lot, but I'll only discuss the Intel SpeedStep technology related aspect. To understand this tool, I need to also explain how Microsoft chose to name the various possible performance settings for your processors - which of course were different than what we called them within Intel (at least in my group).

What the processor does Microsoft's nomenclature What we called it in Intel
CPU(s) run in highest performance state None HFM (Highest Frequency Mode)
CPU(s) intelligently select a performance state based on demand Adaptive Adaptive, SpeedStep
CPU(s) run in lowest performance state Constant LFM (Lowest Frequency Mode)
CPU(s) begin in lowest performance state and then get slower and slower via software manipulation Degrade Why are they doing that?!

One of the oddities was that Microsoft clearly didn't trust that Intel had done their homework and selected a LFM that resulted in the lowest reasonable power consumption. Does throttling the processor even more help save power? Not really - maybe a few more drops could be squeezed out, but the response and performance of the processor is noticeably compromised through their wonderful "degrade" technique.

Anyway, you can use the following command from the Windows XP command line (Start -> Run… -> cmd) to look up the settings of any power scheme (even ones that Dell made for you…):

POWERCFG.EXE /QUERY power-scheme

where power-scheme is the name of the power scheme you want to inspect (like Portable/Laptop).

You can use:


to list all the power schemes currently on the machine.

From the query output, the lines starting with "Processor Throttle (AC)" and Processor Throttle (DC)" will tell you what mode the processor will be in when the laptop is plugged in (AC) and on battery (DC). To change the setting, you use the /CHANGE parameter. For example (all in one line - not two):

POWERCFG.EXE /CHANGE Portable/Laptop /processor-throttle-dc CONSTANT

95 comments to Intel SpeedStep, Windows XP, and confusing Power Profiles

aparent, September 30th, 2007 at 12:10 pm:

  • Thank you! I never understood exactly what each setting means. This is really helpful.

Angel Matos, September 30th, 2007 at 12:21 pm:

  • Thank you for you time and effort. You piece was most informative, most excellent!

    again, much thanXs,


THarrell, September 30th, 2007 at 12:45 pm:

  • I just snapped up a new Dell laptop with a Core Duo in it. Very nice tech on Intel's part. I refused to pay Microsoft to further beta test Vista, however, and I opted to get Windows XP on it. I was well aware of the information given here, but I had fully expected that, by now, Dell would have included a tool to better control battery life! I'm equally surprised and dismayed that Intel does not offer any sort of tool to manage the battery saving features offered! I ended up finding a very useful little tool written as freeware by a kind individual out there which allows explicit control over automatic clock-throttling. Also, this independent program allows for automatic voltage throttling as well. I'm extremely disappointed with Microsoft, Dell, and Intel alike, as I don't believe voltage-throttling is available at all by using only vendor-supplied tools, though it has been a staple of Intel's battery saving technology since the Pentium 4 Mobile!

Alex, September 30th, 2007 at 1:01 pm:

  • An informative story indeed, I often thought about the difference between those items. I have empirically reached the conclusion that "portable/laptop" was the optimal choice for me, but deep inside there was always a grain of doubt. Thanks for clearing things up.

James, September 30th, 2007 at 1:06 pm:

  • Should point out that there's a great program out there called "Speedswitch XP" that further exploits what you are able to do with power saving settings. Some of the profiles don't allow for finer adjustments. Speedswitch allowed me to adjust every single option within the power schemes in WindowsXP. (ie, you're now not limited to what each of the profiles in Control Panel were set to do)

DigitMemo.com » Processor Throttling In Windows XP, September 30th, 2007 at 1:16 pm:

  • […] summary of Windows XP power schemes as they relate to Intel processor throttling. Old topic, but one still relevant as many business notebooks still use […]

C. Shamis, September 30th, 2007 at 3:00 pm:

  • This is why I think my next machine is going to be a mac. I'm just tired of having to do all this stuff for myself all the time. I mean really, why should I have to be an expert on CPU duty cycle throttling just to have a quiet computer? I mean shouldn't the CPU and OS mfg know how to throttle down the CPU when there is no reason for it to be running flat-out?

    For crying out weve been making furnaces for 100 years that know how to adapt to a duty load… Why is my computer so brain dead? Its inexcusable really… Moreover I should not have to be the guy who has to read articles like this to figure out how (or what) is going on… Isn't that what I paid for when i bought the the OS? If i wanted to be in charge of everything on the box I'd write my own OS from scratch!!!! I don't need to spend my hard earned money on the "latest" version xyz !!! I bought the stupid thing to do a JOB! Quite frankly I'm getting disgusted with the whole scene…

Uh Duh, September 30th, 2007 at 3:07 pm:

  • "This is why I think my next machine is going to be a mac. I’m just tired of having to do all this stuff for myself all the time. I mean really, why should I have to be an expert on CPU duty cycle throttling just to have a quiet computer? I mean shouldn’t the CPU and OS mfg know how to throttle down the CPU when there is no reason for it to be running flat-out?"

    Uh, the Mac didn't have CPU throttling capabilities until they started shipping with the Intel CPUs…
    Learn to use your computer and you won't have to get a Fisher-Price equivalent to do magical stuff.

Michael Chu, September 30th, 2007 at 4:08 pm:

  • Concerning voltage throttling:
    If I recall properly, before I left Intel, all the processors that supported multiple voltage points changed voltage automatically with frequency. If the operating system enabled SpeedStep, then the voltages would change appropriately. There's not really a benefit to manually controlling the voltages separately - we had a whole team working on the power curves and testing various scenarios to figure out the best combinations for not just power savings but also robustness.

Sherpa Josh, September 30th, 2007 at 4:37 pm:

  • I like to use Notebook Hardware Control to control my processor. In addition to the processor it can also adjust the graphics card performance if you have a Nvidia card. You can also overclock or even underclock the processor. Great program and always one of the first programs I install after a format. http://www.pbus-167.com/

Aaron Hayes, September 30th, 2007 at 5:17 pm:

  • This is how AMD's PowerNow! works as well.

    I used to get the same efficency out of my A64 notebook as a Centrino notebook with this enabled.

Mohd. Hashim Khan, September 30th, 2007 at 5:32 pm:

  • Looks something similar to AMD Cool n Quiet technology which is for desktops as well.

Jay Lee, September 30th, 2007 at 8:21 pm:

  • I recommend RM Clock to handle throtling and such in windows. I have it configured for my laptop and it works perfectly. Tons of options to play with too.


    (I am not affiliated with this product, it's just good)

一亩二分地 - 笔记本的电源管理设置, September 30th, 2007 at 10:03 pm:

  • […] Chu写的关于笔记本电源管理的文章, 起因是他老婆抱怨笔记本的风扇很吵总是不停的转. […]

Sam, October 1st, 2007 at 1:12 am:

  • Perhaps Microsoft's "degrade" setting is meant to give some benefit for non-speedstep processors? No need to get offended….

Andrew Hood, October 1st, 2007 at 1:13 am:

  • Interesting article, thanks.
    But how do these settings affect other Intel processors? Is it the same with the core duos? And is any throttling possible on desktop P4s?

links for 2007-10-01 « xtra’s blog, October 1st, 2007 at 1:22 am:

  • […] Intel SpeedStep, Windows XP, and confusing Power Profiles | Orthogonal Thought (tags: Windows power laptop battery xp cpu Hardware utilities windowsxp tutorials tools winxp) […]

Adrian O'Connor, October 1st, 2007 at 1:42 am:

  • It's really interesting to finally learn how Microsoft's power schemes affect the adaptive frequency of our processors.

    An excellent product that helps you control the processor throttle settings in Windows XP is SpeedSwitchXP (http://www.diefer.de/speedswitchxp/) - it is a close replacement of the Intel SpeedStep utility that I so loved in Windows 200. It lets you change the CPU throttle mode on the fly.

    It's worth noting that Linux out of the box runs noticably cooler and battery life is significantly longer on a Petuim M laptop - I guess the Linux engineers trust Intel's SpeedStep and just let it do it's thing.

Esquemes d’energia de Windows XP * L’home dibuixat, October 1st, 2007 at 3:36 am:

  • […] article, Intel SpeedStep, Windows XP, and confusing Power Profiles, on s'explica de forma clara que fan els diversos esquemes d'energia que incorpora […]

Marcello Romani, October 1st, 2007 at 10:59 am:

  • Thanks for the information provided. This article was helpful to me.

/++//++//++//++//++//++/ » Blog Archive » Tips: tweak your computer, October 1st, 2007 at 11:18 am:

Intel Speedstep Infos - Das3Zehn Blog, October 1st, 2007 at 1:21 pm:

  • […] 01. Oktober 2007 Netzkram, Technisches Vielleicht für den einen oder anderen Notebook-Besitzer interessant, welcher Windows XP fährt und einen Intel Prozessor in selbigem verbaut hat: Eine richtig gute Informationssammlung zur Intel Speedstep Technologie sowie den Windows XP Energiespaar-Einstellungen. Klick mich […]

Neil, October 1st, 2007 at 6:27 pm:

  • Actually, Intel's power-saving by throttling the CPU load back is an ugly hack. I don't think that it's completely worthless, but it's still an ugly hack. Motorola's Power PC chips originally pursued a design of low power usage, but as the PPC business alliance disintegrated, and IBM kept pushing the performance envelope for server applications, the PPC architecture just got more and more power hungry. The final Mac generation, the G5, made an awesome workstation platform, but Apple could not shoehorn it into a portable.

    The correct approach to power-utilization problems is to push for chip efficiency. Running full-on top-speed at all times is pretty dumb - but intel isn't pushing efficiency either - they're throttling back to save energy. Now; if I have to do X amount of work, and I have Y time to do that work, and if I'm on battery, you slow my CPU down, I'm not going to get that work done any faster. . . either the battery is going to do the job for me or not. Slowing my machine down does not solve this problem. Giving me a CPU that does more with less power (Transmeta!) solves my problem.

    Given that Motorola and Transmeta tried to solve this problem (and gave up) - I can't really credit them much more than Intel. I hate their approach, but at least they did *something*.

Michael Chu, October 2nd, 2007 at 12:37 am:

  • re: Core Duo's and Pentium 4 (desktop parts)
    SpeedStep is fully functional on multi-core (dual- and quad-core) Core Duo and Core 2 Duo mobile processors from Intel. If I remember properly (and it has been a couple years since I looked at this), the cores can drop frequencies not just from HFM to LFM but also intermediary points. Voltage also drops appropriately and the processor clocks also stop when there is no load.

    re: Neil's comments on Oct. 1 at 6:27pm
    Going multi-core has saved a lot of power, but SpeedStep is a pretty decent solution. Your example of X amount of work in Y amount of time is a valid one, but if SpeedStep is allowed to do its thing (Microsoft calls this "Adaptive") then the system will be in LFM when idle (in fact, the clocks will be stopped since the processor will enter ACPI C4 state) and when a computational task is provided, then the processors will hop up to a higher frequency to complete the task as quickly as possible. At high performance, the Intel CPU's are quite efficient when measured by instructions/watt. It does drop to LFM after the computation because most of the time there just aren't many instructions to be processed (since the computer is waiting for the user to do something - type a key, click something, etc. - for 99% of the time). Now, if you mean you (personally) have X amount of work to do (and not the CPU has X amount of work to do), then most of the time the CPU should be in LFM and with it's clocks stopped. Slowing the machine down does make sense (as long as it can still speed up to do the few computationally intensive tasks). That's why I generally recommend "Portable/Laptop" as your power scheme, so the processor is allowed to do what it's designed to do.

  Processor Throttling dan Batere Notebook — Technica at Blogpunk, October 2nd, 2007 at 5:03 am:

  • […] ini bisa di setting di power schemes (Control Panel -> Power Options -> Power Schemes). Blog ini mengungkapkan apa sih arti dari pilihan2 di power schemes di […]

Processor Throttling In Windows XP | Amephist Feeds, October 2nd, 2007 at 8:19 am:

  • […] Chu, a former Intel employee, has written up a fairly interesting and readable summary of Windows XP power schemes as they relate to Intel processor throttling. An old topic, but one still relevant as many business notebooks still use […]

Jon G, October 3rd, 2007 at 4:16 am:

  • I second Notebook Hardware Control (NHC) at http://www.pbus-167.com/

    On AC, my laptop is set to Dynamic Switching so it doesn't heat up when idle.

    In addition, NHC allows overriding the voltage, which is useful for undervolting. This allowed my 2-year-old Thinkpad to last about 2.5 hours on a full charge, despite about 30% of battery wear.

Jeff M, October 3rd, 2007 at 11:13 am:

  • Very nice article. Let me ask you this though, when set to adaptive is the OS managing the power state or is it the chip itself? I found myself adjusting this to none while using AC on most of the laptops because the the technology or the implementation of it wasn't working well with XP. To be more specific, laptops using adaptive mode would run at nearly half of their true speed during the windows boot-up / login process which significantly reduced the performance when it was really needed. I would have assumed that the cpu or the software managing the throttling would have been able to correctly determine the load on the processor and bump the speed while boot / login occurred. In this case, where would the faulty logic lay?

george trikardis, October 3rd, 2007 at 4:14 pm:

  • Thank you so much for clearing this up. I've been trying forever to find a solution for my dell which , when docked, doesn't work at its full 2.13Ghz capacity. How can I force change to the max cpu frequency possible? it's an always-docked system so thats what I need.

    I read that this is the desired scheme I need:

    CPU(s) run in highest performance state None HFM (Highest Frequency Mode)

    so how should I form the following command?
    POWERCFG.EXE /CHANGE "Always On" /processor-throttle-dc None ?

    Please advise!! thanks

Michael Chu, October 3rd, 2007 at 5:01 pm:

  • re: Dell docking HFM

    If you're using Always On, then when docked it should be in HFM mode unless there's another battery management utility running (like Dell Quickset) that may be overriding the choice. You may have to dig through the various utilities that are running and see if you can find additional power management options (specifically for your docking).

    As to your POWERCFG.EXE command, it's not correct - docking is AC not DC (DC = running on batteries; AC = plugged into wall; it's a weird convention since it's all DC entering the laptop, but that's how it's labeled). So the command should be:
    POWERCFG.EXE /CHANGE "Always On" /processor-throttle-ac NONE
    (which is the default setting for Always On anyway)

Maktoum, October 4th, 2007 at 2:43 am:

  • Thank you kindly for your most informative contribution! Finally I know how to manipulate the OS to stop manipulating my CPU speed!! I have been searching for months for a solution that would enable me to set my Pentium M to full throttle and force it to stay there. I am greatly indebted to you!! I would send you my sister in gratitude had you not already been wed…
    As-salaam alaykum — Peace be with you!

CSC Blog » Blog Archive » XP Fo Life, October 4th, 2007 at 9:33 am:

Tobias, October 8th, 2007 at 8:52 am:

  • I have a question. I have a laptop with a quite powerfull CPU. Can this be used to slow down the CPU to make the computer less hot and therefore less noisier?

    Pardon my english!


Martin, November 28th, 2007 at 12:22 pm:

  • Does anyone know of a way to query a laptops battery status (remaining time/percentage etc)from the command line?

我们的空间 » Blog Archive » 笔记本的电源管理设置(转), December 13th, 2007 at 6:36 pm:

  • […] Chu写的关于笔记本电源管理的文章, 起因是他老婆抱怨笔记本的风扇很吵总是不停的转. […]

Alexander, December 13th, 2007 at 11:06 pm:

  • Thank you for the article, it's very informative.

    Recently I found that my Pentium M Dothan 1.73 works only at LFM and HFM, without any other frequencies in between with different CPU load. Power scheme is Portable/Laptop.

    Do you have any ideas why is it so?

Michael Chu, December 17th, 2007 at 6:09 pm:

  • Although Dothan supports multiple frequency points, in most cases it is advantageous to be in either HFM or LFM. Time spent in intermediate frequencies is generally fairly low and hard to catch - especially with the Windows frequency reporting tool that polls about once a second.

Ken, December 30th, 2007 at 3:48 am:

  • I have lost the control panel power schemes somehow when I removed a mouse utility.

    Does anyone know how to reload the power schemes for the laptop? - I have a Dell xps m140 running XP professional.


Peter, January 4th, 2008 at 5:37 pm:

  • Did you get the info on how to restore the power schemes? If so would you please share it with me. Thank you.

Jay, January 23rd, 2008 at 11:01 pm:

  • I really liked toshiba's power saving program. Very simple to use and very effective. I wish i could put that on all my laptops. Ithink it was called Power Saver. Loved it.

Dr-KDE, January 27th, 2008 at 4:33 am:

  • Many Thanks, well written.

What to do when Intel SpeedStep is really, really broken on Rantings of a Grooveshark Dev, February 9th, 2008 at 4:03 am:

  • […] For a while I blamed the BIOS, thinking that even though I had it enabled in the BIOS something was getting messed up at that level. Today I updated my BIOS and installed a new CPU (3.0GHz, 6MB cache C2D FTW), and it was still not SpeedStepping when it should have. So I did some more digging and found this page all about Intel SpeedStep. […]

Green Blog » Blog Archive » Change your Windows XP Power Profile to save energy, March 2nd, 2008 at 5:19 pm:

  • […] more: Intel SpeedStep, Windows XP, and confusing Power Profiles Tags: AMD A64, AMD Athlon XP, computers, CPU, energy saving, green tip, Intel Core, Intel Pentium […]

Noxic, March 17th, 2008 at 6:13 am:

  • Is this all about a Dell Laptop, What about a 2005 Desktop Intel Pentium D Dual Core 3.0GHz Processor, i have Speedstep turned off in the BIOS but it enables again in XP? can i fix this problem?? (i want my computer to have full trottle all the time.


Michael Chu, March 17th, 2008 at 9:05 am:

  • If SpeedStep is disabled in BIOS, then no software (OS) settings should be able to enable it (assuming the BIOS is properly implemented). However, simply setting your Windows XP power scheme to Always On should have your desktop in HFM (High Frequency Mode) all the time. How are you determining that your system is throttling its frequency?

mathieu, March 26th, 2008 at 1:03 am:

  • Thanks for these informations .
    I use my Centrino laptop as a DAW for recording multi-tracks audio. In several audio sites there are tricks about turning off Speedstep to be sure that the processor will always be at max performances. I did that (before reading your article…) and i found that the result was very bad. It seems that disabling speedStep in my bios blocked my processor in LFM mode. Enabling SpeedStep and using an office desk scheme seems to be ok. So what happends if SpeedStep is disbled in the bios ?

Michael Chu, March 27th, 2008 at 12:53 pm:

  • Depends on the BIOS and how the manufacturer decided to program it. The manufacturer can choose to put the processor in LFM or HFM mode permanently on boot up, but I don't see why they would choose LFM… Many laptop BIOSes are based on the Phoenix BIOS and that one defaults to HFM when "Intel SpeedStep technology" is disabled (if I recall correctly). Of course, you have to remember that the BIOS setup screen is just a user interface and the words shown there are written by the manufacturer or BIOS vendor and don't necessarily map to specific Intel registers…

Naren, April 18th, 2008 at 10:40 am:

  • Thanks for the information…Really helped us resolve a mystery that we have been fighting on for days!!

Windows XP, April 28th, 2008 at 5:20 pm:

  • Thank you for this information! It really helped me learn what I had been pondering. And to let you know, it was the SpeedStep. :P

Steven Cyzner, May 16th, 2008 at 1:07 pm:

  • The above url really is not MY website as you well know. I have a problem: I deleted my Home/Office Power Setup and now have no access to setting up another one. I had created some others but they aren't to be found. Those boxes are now grayed out.
    What can I do?

Michael Chu, May 17th, 2008 at 11:00 am:

batteries, June 1st, 2008 at 6:07 pm:

  • Thank you for this outstanding article.I thought Centrino was the best technology for laptop battery performance.

Disable Dynamic frequency in XP, June 23rd, 2008 at 3:47 pm:

  • Hey,
    Thanks for these very very very useful and quick infos!
    I have been trying them and they work just fine( voltage drops with respect to the chosen scheme….), but I have 1 problem:
    I set the processor-throttle-ac/dc = NONE and the frequency of the CPU is still dynamic(speedstep enabled???), while the voltage is static(having the max value)!!!….How is that possible?!
    The system is a HP 530 laptop with CPU Core Duo T2600.
    I have used everest lavalys and cpuz to view the voltages and frequency.

    Thank you

Michael Chu, June 23rd, 2008 at 11:02 pm:

  • If I remember correctly (and it's been a few years since I worked on this stuff), the manufacturer can override Intel SpeedStep technology settings by programming registers in the BIOS. There might not be a way for you to have complete control through software/OS if this is the case.

gyrfalcon, September 19th, 2008 at 6:27 am:

  • Hello Michael,
    Thanks for the great article! As the poster above mentioned, they processor throttle to none and speedstep was still enabled.

    I'm using a Thinkpad T60 and I'm having the same issue. I don't believe the BIOS has a flag to control this information on this system.

    So right now I'm kinda wondering what's going on and why the Powercfg settings are not kicking in. Maybe a reboot is necessary? I'm running Windows XP SP3 and pulling the speed with CPU-Z.

Michael Chu, September 19th, 2008 at 11:01 am:

  • It's been a few years since I worked on this - there might be a way in BIOS (not the BIOS setup, but the actual BIOS code of the system that you can't modify) that forces Intel SpeedStep technology on regardless of the OS settings… If this is the case, you might not be able to turn it off at all.

    Rebooting should not be necessary for POWERCFG changes to be applied.

Bios or OS, October 31st, 2008 at 10:07 pm:

  • Actually I'm a bit confused which setting trumps which setting? The bios or the Windows XP. From what I can determine it's entirely up to the program coder and theres no method or verify which supercede the other. Anyone have a better idea/determination.

Michael Chu, November 1st, 2008 at 1:10 am:

  • There's no way to really tell which trumps which because we don't know how the BIOS is implemented. There are registers in the CPU that the BIOS writes to to set various settings which include disabling Intel SpeedStep technology (and setting the frequency/voltage permanently to a particular level) and enabling it but limiting it to certain frequencies (and/or voltages). In the BIOS setup, usually it just says "Enable SpeedStep" or something like it, but you don't know what HP or Toshiba or Dell decided to actually program the CPU to do. The OS cannot really defy the CPU settings (there are some ways around it) - so if the BIOS has programmed your system to not have SpeedStep enabled and to always be in Low Frequency Mode, then no matter what the OS tries, it will be in low frequency mode. Fortunately or unfortunately, the BIOS menus don't give you this level of control (or information) and the manufacturer has selected two or three choices that they've tested thoroughly in their build. These settings are almost always more complicated than the one line description you get in the BIOS setup and in most cases we can't predict if the OS can override the apparent setting we chose in the BIOS setup.

anth, November 3rd, 2008 at 4:52 pm:

  • Mate,

    This was the simplest, yet mostest extremeliest and amazingest help I could find.
    I work with music production, and just got a new Laptop in which I use Ableton Live. Its a duo core super slick lappy, and it the CPU in Live in my new projects was just blowing off the roof, and having spurts of
    erratic glitches…
    I just swithced to office/desk option and its all stable now…
    brilliant…just brilliant..

Gary Cunningham, November 10th, 2008 at 4:37 pm:

  • Thanks for the info. Recently my notebook has started shutting down when running on AC. Usually while watching video's or other high processor demand apps. Using powercfg I created a new power profile throttling the processor down to "constant" on both AC and DC. No more problem and the fan almost never comes on anymore. Other than that I can detect no difference in performace.

randy repp, November 28th, 2008 at 11:33 am:

  • i have accidently changed the default XP SP3 Home/Office Desk power scheme settings; does somebody have those default settings? i think they were this:

    plugged in:
    monitor: 20 minutes
    hard disk: 1 hour
    standby: never
    hibernates: never

    monitor: ?? minutes
    hard disk: ??
    standby: ??
    hibernates: never

Pierre, April 25th, 2009 at 7:41 am:

  • Michael, many thanks for your info, and I have noticed that
    when my laptop is in DC mode(battery), the CPU seems to restore to HFM not as fast as it is with AC on. When with AC on, it restores to HFM much more smoothly than on battery. BTW, while both AC and DC mode are set to use "always on" power management scheme, I guess my BIOS has still force the cpu to use speedstep all the time.
    The suspect I got is a Flash pool game(played with Macromedia flash player 8) with RightMark CPU Clock. This game demands CPU so differently at any time that the RM CPU Clock drops and rises some times. When in AC mode, it restores from LFM to HFM very quickly. When in DC mode, however, it restores to full speed very bluntly, which causes the running balls freeze on the screen for about a half second! It is so apparently that any one won't ignore!
    My CPU: Intel Core 2 Duo P8400
    Laptop: HP 6531s

    My question is: Whom is to blame for this issue, BIOS coding or CPU throttling mechanism ? Please help! Thanks a lot!

Michael Chu, April 25th, 2009 at 10:51 am:

  • Pierre, I know I'm not addressing your question (because I don't have an answer), but I wanted to say that modern CPUs (Pentium M and later) that support SpeedStep perform frequency switching very, very fast. We're talking microseconds. If you see a half second delay, then that's something else. The system might be doing frequency switching but it must also be doing a lot of other things (perhaps HDD spin up/down).

Pierre, April 26th, 2009 at 9:18 am:

  • Michael, thank you for your quick reply. I know the speed should be just few ms, and so neither do I believe the 500 ms delay was caused by SpeedStep. (I asked this just to make sure)
    Now the question may be why the awaking time differs so much in AC and DC mode in my case? This 278kb game doesn't have a lot of HDD task, and to exclude such factor entirely, I tried to run the swf file on a RAM disk, and still got the same result: More delay of awaking time still occurs when in DC mode. It appears to be a CPU or GPU delay(But either do I set my video adapter's power management profile to maximum performance, it makes no difference). Will there be a case that some delay on awaking from LFM in DC mode is a design to enhance power saving (According to Intel, P serials have more power efficiency among Penryn products)? Or will there be a reason for BIOS to do this?
    Hope I make my question clear, and any help is much appreciated!
    (BTW, I found I solved this with a new version of Adobe Flash Player (v10), and there won't be any "apparent" difference in awaking delay, i.e. the ball runs smoothly both in AC and DC mode.
    So it could prove that my CPU's awaking delay from LFM is consistent in both AC and DC mode.
    But why version 8 player shows apparent lag from LFM in DC mode is still a hard nut to crack for me….)

Michael Chu, April 26th, 2009 at 8:35 pm:

  • I'm not sure how long lane switching takes (shouldn't be 500 ms!) but it could be your GPU going from low power PEG x1 to PEG x16 mode contributing. I'm not familiar enough with Flash to know what differences were introduced between 8 and 10… Perhaps it has nothing to do with power management and more to do with graphics acceleration support in Flash 8 and weird computational bottlenecks (that the CPU had to handle but doesn't in Flash 10)?

Pierre, April 27th, 2009 at 8:12 am:

  • That could be the case….but still, why the bottlenecks only exist in DC mode (with "always on" set)? It's really weird…
    (and why it doesn't exist any more in Flash Player 10's Action Script interpretation)
    Thank you for show me some possibilities to think about. Maybe some relevant tools are need to do further survey.

Jase, April 29th, 2009 at 4:37 pm:

  • This is one excellent passage.

sucipto, May 5th, 2009 at 5:27 pm:

  • Many thanks to you michael. My intel atom is slow on my first try, that it's frustrating, it run only 797 Mhz or so. But when it run full speed (always on), it's as fast as my Celeron (conroe) desktop. What power scheme does MS has on vista or 7 ??

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rapitu, October 16th, 2009 at 8:08 am:

  • Thanks for the info. But what does "CPU(s) begin in lowest performance state and then get slower and slower via software manipulation" exactly mean? It sounds like my laptop performance will decrease while I use it ¿?

Michael Chu, October 16th, 2009 at 10:10 pm:

  • In degrade mode, the CPU is set to its lowest frequency. Then the operating system attempts to further throttle the CPU by applying the STP_CLK (stop clock) signal. Given that modern CPUs enter C3 or lower sleep states automatically, this "degrade" setting doesn't help save power much. In fact, it can slow down computation, requiring more power to perform the same tasks over time.

Theo, November 15th, 2009 at 1:34 am:

  • Very good info!
    Do you know a utility to read the cpu temperature and voltage in a laptop running XP? Thanks.

Bram, December 23rd, 2009 at 7:39 am:

  • Hi,

    I'm experiencing serious issues with my Dell Inspiron 9400. Since 2 weeks my CPU only works at 1000 Mhz of the 1,66 Ghz.

    I have disabled Speedstep in my bios, flashed my bios to the latest version en put the settings to "Always on". But still it only runs at 1000 Mhz.

    I use CPU-Z to read the Corespeed of my CPU.

    In bios is stated that the processor speed is 1000 Mhz, however, when I look at the Preferences of My computer there is stated that the computer runs at 1,66 Ghz. Anyone has an idea what the problem could be?



Customize your laptop speed for temperature and performance | All My Brain, January 15th, 2010 at 9:09 pm:

  • […] gist of the article is that you can't directly control the algorithm being used with the Windows XP power properties. […]

Use SpeedStep to Minimize Fan Noise even while laptop is plugged in – via Win XP command line « Some ideas and thoughts of G.B., February 4th, 2010 at 2:35 pm:

  • […] can head over to Orthogonal Thought: Intel SpeedStep, Windows XP, and confusing Power Profiles and read what profiles does what. If you want a profile that throttles the CPU all the time, do the […]

Mike, February 17th, 2010 at 5:55 pm:

  • Thanks for the concise and informative article. I'm "cousin IT" for my aunt and uncle–now I can go set their Power Management properly, instead of guessing.

valeria mendoza, July 2nd, 2010 at 7:59 am:

  • speek spanish and english need more information of the tecnology intel and of the Processors

Brandan, September 13th, 2011 at 7:38 pm:

  • Hello There. I discovered your blog site using msn. This is the pretty nicely created article. I'll be sure to save it and return to study further of the practical info. Thanks for the posting. I'll probably certainly return.

Daniel, May 11th, 2012 at 11:34 am:

  • I was looking for this information since I discovered that the CPU didn't reduce the CPU speed… I had changed the configuration…. Now I understand why exactly and how I can solve it, Very good article. Thanks!!!
    Use everybody "Portable/Laptop" !! :-)

Chris S, June 14th, 2012 at 9:45 pm:

  • 5 years later and your article is still helping people!

    I was able to configure my laptop to use ADAPTIVE which really helps me save battery.


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