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Windows Operating Systems Software Hardware

Processor Throttling In Windows XP 148

TomSlick writes "Michael 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 XP."
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Processor Throttling In Windows XP

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  • For a second there, I read "Professor Throttling in Windows XP"
  • Nice (Score:5, Interesting)

    by teebob21 ( 947095 ) on Sunday September 30, 2007 @02:28PM (#20802807) Journal
    Now I know why my laptop burns my legs whenever I use it...it literally IS always on...so that's what my power management was set to. I had no idea that affected the CPU frequency stepping. I guess i just had assumed that was something that scaled intelligently depending on load average or some other *CPU* metric, not a battery setting.

    Of course, being WinXP, I should have realized that Foo is actually changed each time I use the GUI to modify the behavior of Bar 1 and Bar 2, which are completely separate system functions.
    • Re: (Score:3, Insightful)

      by xtracto ( 837672 )
      Yeah, I have known about this stepping options back when I used WinXP in my laptop, the program CPUZ shows quite interesting information and the current running frequency is one of them. What I did not know is how to manually change this profiles... [un]fortunately I am now running Ubuntu and I guess there is no easy way (not requiring a kernel patch or some magical .conf file mangling) way to set my computer to a low speed as in Windows.
      • Re: (Score:2, Informative)

        by Anonymous Coward
        There is a program called cpufreq-selector that should come with the default installation. There is even a Gnome panel applet that interacts with it called CPU Frequency Scaling Monitor.
      • Re:Nice (Score:5, Informative)

        by EvilIdler ( 21087 ) on Sunday September 30, 2007 @03:21PM (#20803125)
        Sure you can:
        cpudyn - CPU dynamic frequency control for processors with scaling
        cpufreqd - fully configurable daemon for dynamic frequency and voltage scaling
        cpufrequtils - utilities to deal with the cpufreq Linux kernel feature

        All are found in your apt repository.
        • And you should add, any number of power management apps will handle all that for you automatically. For me, I use kpowersave, and it handles cpu frequency scaling and power profiles (performance/dynamic/energy saving) for me.
      • On Debian, all I had to do to get processor throttling working was apt-get install powersaved.

        Now, my 2ghz Core 2 Duo has both cores running at 1ghz, except when the full 2ghz is required. This + i8kutils to force my left fan to run on low all the time = 26C when idle. Not bad for a dual core system. :)
      • Gnome power manager has looked after cpufreq scaling since at least Edgy. You can choose between three profiles - always high, always low, or on demand.
      • ``[un]fortunately I am now running Ubuntu and I guess there is no easy way (not requiring a kernel patch or some magical .conf file mangling) way to set my computer to a low speed as in Windows.''

        Why do you assume that something is difficult on Ubuntu? And what is difficult about editing configuration files?
        • by xtracto ( 837672 )
          Why do you assume that something is difficult on Ubuntu? And what is difficult about editing configuration files?
          Because Ubuntu is Linux after all, and for example, I have just tried to install truecrypt and, while in windows is just a matter of double click an exe ant then load a nice interface, there is no such thing as a nice interface and you need to do all kinds of su a+x truecrypt bash things (I know how to do it... after all I work with bash/awk/R/Java/C++/JNI/Latex every day).

          But the main difference
      • Damn. It only took 4 mouse clicks to enable this on my Ubuntu on Compaq laptop. I didn't even have to edit the .conf files except I wanted it to always run in a low power mode while on battery (locked it to 1 Ghz).
      • First of all, if you want interesting information:

        cat /proc/cpuinfo

        The speed listed there is, in fact, your currently running speed.

        But more relevantly: I've installed Ubuntu Feisty on three machines now which had CPU scaling -- two separate AMD desktops (one dual-core, one single-core) and one Intel laptop (dual-core). On all of them, CPU scaling was automatically detected and enabled, in a reasonably intelligent manner -- most of the time they all run at 1 ghz, but they can and will crank up to 1.8, 2.0,
  • I don't run vista. Could someone try following the paper in vista and explain any differences?
  • by istartedi ( 132515 ) on Sunday September 30, 2007 @02:37PM (#20802873) Journal

    For a while, I thought my fan might have been broken because my laptop was getting very hot. Then I realized that, a few months ago I had messed with the power setting and turned off that technology to make sure I was getting maximum performance out of something. I forgot to turn it back on, and this resulted in the machine running flat-out all the time and getting very hot. Something jogged my memory, I went back to the power settings, and it works fine now. Even DVD playback doesn't force it to run flat-out, so if you have this technology you should definitely use it.

    Of course it's only easy to feel the heat with a notebook. If you have a desktop you could be wasting power and not even know it unless you check the settings.

    • by zlogic ( 892404 )
      If you have a relatively new system with automatic fan control (late Pentium 4, Pentium D or any Core), you'll definetly hear if it's wasting power :-)
      And desktop Cores can actually lower their frequency when CPU load is low.
  • ... with AMD Cool'n'Quiet in Windows XP Pro. SP2 even with the latest drivers on my Athlon 64 4600+ (939 dual core) system. It seems like I would get rare random blue screens of deaths (IRQL_NOT_LESS_OR_EQUAL) when playing videos. One time, I had a corrupted SB Audigy 2 ZS driver and I had to reinstall it. I don't have this problem if I don't use the power management (Cool'n'Quiet).

    No one was able to figure out why I get them according to this newsgroup thread [google.com]. Maybe it is because of all my hardware devices
    • It seems there are some problems with cool'n' quiet and some hardware. My Nebula TV tuner card was getting random glitches when watching live TV or recording. I have a 939 Athlon single core and an Asus A8V board in my PVR, and it worked fine when I turned that feature off in the bios. Try removing the TV card and seeing if the problem persists.

      On my Linux box, it seems to work fine. The boot up for Fedora 6 complained quite a bit when I didn't have it enabled, and it throttles the CPU speed quite nicely to
  • by pla ( 258480 ) on Sunday September 30, 2007 @02:44PM (#20802927) Journal
    If you run XP, set the power scheme to "Minimal Power Management".

    Unless, as a twitch-gamer, you (think you) can't afford to lose even a single CPU cycle, then by all means continue trying to heat your house in "Always On" mode (or the default of "Home/Office Desk", which means the same thing to AC-powered non-laptops).

    As an interesting aside, TFA's author recommends "Portable/Laptop" mode; However, he writes that coming from the Intel world. Users of AMD chips (myself included) have noticed problems with CnQ (AMD's version of SpeedStep) not working correctly unless you set it to "Minimal Power Management", which according to the charts in the linked article, should work the same as "Portable/Laptop".
  • Throttling (Score:3, Funny)

    by Wowsers ( 1151731 ) on Sunday September 30, 2007 @04:00PM (#20803439) Journal
    After using WinXP, it's not the processor that wants to throttle the system - it's me. So I installed Linux instead.
  • by bl8n8r ( 649187 ) on Sunday September 30, 2007 @04:48PM (#20803765)
    as a cpu throttler.
  • by Devistater ( 593822 ) * <<moc.liamtoh> <ta> <retatsived>> on Sunday September 30, 2007 @06:05PM (#20804225)
    Its not just business laptops that are using XP. The vast majority of people still use XP. Heck, even amongst average gamers (where you'd expect ppl to upgrade to vista for DX10 games), less than 2.5% have vista and a dx10 capable card.
  • by Wesley Felter ( 138342 ) <wesley@felter.org> on Sunday September 30, 2007 @07:21PM (#20804663) Homepage
    "CPU(s) begin in lowest performance state and then get slower and slower"

    This is remarkably sloppy writing for a supposedly technical article. Is there a performance state even lower than the lowest? Is he talking about clock modulation? Does it get "slower and slower" but never faster and faster?
  • by ConceptJunkie ( 24823 ) * on Sunday September 30, 2007 @08:17PM (#20804947) Homepage Journal
    XP can throttle your CPU, but Vista downright chokes it.
  • I was quite dissapointed with SpeedStep, especially on dual/quad core processors. The lowest possible multiplier is 6x, which works out at about 1.6GHz, still very high for idling on four or even two cores. I don't see any reason why it couldn't drop a lot lower, if not by default then at least as an option.
  • In soviet Russia, the Processor throttles YOU!

  • 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 in

I just asked myself... what would John DeLorean do? -- Raoul Duke