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  1. #1
    New Lounger
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    Dec 2009
    Naperville, IL
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    CPU Utilization at 100% - 76% by "Interrupts"

    I have this issue with one laptop and one desktop PC, both Win XP SP3.

    The laptop is an early Asus machine that the system fan quit working and I can't find a replacement. I'm not even sure I have booted that system in over a year.

    The desktop PC is a Pentium D 820 PC that I built myself.

    The symptoms are, I am either using the PC or waking it up from a period of no user input.

    Everything crawls to a refresh, Process Explorer shows the top resource hog to be:
    Interrupts 75.92% Hardware Interrupts and DPCs
    (It varies from like 62% to 95% -- it isn't locked on the 76% number.)

    On the desktop PC the fans all spin, I have upgraded to a new 750W power supply.

    I don't see any capicators with their tops blown off on the motherboard or any of the PCI add-on cards.

    I am usually using Internet Explorer 8, but I don't leave it up when I leave the machine.

    If I reboot, either a "soft" restart or a power interruption, the problem goes away for the rest of the day and the system works wonderfully. If I leave it up, the problem will resurface in the next day or two.

    One thought is that Norton Antivirus is scanning the files on an attached USB drive, but none of the Norton process are even in the top 5 when this slow-down happens. The interrups continue to happen at the same rate if I unplug the USB hard drive, and it will go into the same state in a couple of days if I boot the PC without the USB hard drive attached.

    Any clue as to what causes the Interrupts?

  2. #2
    Super Moderator CLiNT's Avatar
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    Dec 2009
    California & Arizona
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    It sounds like a problem related to power management/sleep/hibernation

    restore default power settings in XP

    Use the Powercfg.exe utility to restore the default power scheme

    You can use the Powercfg.exe utility to copy the power scheme from the Default Userprofile to the user who is currently logged on. You can do this because power schemes are uniquely associated with individual user accounts. To copy the power scheme from the default user by using the Powercfg.exe utility, follow these steps:
    1. Click Start, click Run, type cmd, and then click OK.
    2. At the command prompt, type the following command, and then press ENTER:
      powercfg /RestoreDefaultPolicies
    Ensure that the computer(s) in question have bios that support S3 functions.

  3. #3
    Lounge VIP bobprimak's Avatar
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    Feb 2009
    Hinsdale, IL, USA
    Thanked 157 Times in 131 Posts
    With all those hardware upgrades, CLiNT may be onto something. Sometimes Windows (or an older BIOS) does not adapt automatically to changes in power supplies or other hardware. And when the system fan stopped working, heat might have caused some unobvious damages. Hardware diagnostics should be run if CLiNT's suggestion doesn't solve the issue. Bigger power supplies require better cooling, so the heat issue may have returned in that way.
    -- Bob Primak --

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