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A few times a day my CPU will jump to 99% usage, and it will stay there until I force a shutdown (via unplugging it). Below is a snap of the task manager during this time. I am certain a virus is not the problem. update I have found I can reproduce the problem by putting my network card under load. I have tried 3 different wireless cards (usb adapter), and it happens will every one of them.

What is installed?

  • Firefox 3.5
  • Chrome Beta version
  • MS Security Essentials
  • Win 7 Ultimate (64bit)

I would assume there is a faulty driver, but I have no idea where to start. Does anybody know what the best thing to do is in this situation?

updated the screen shot to show process explorer while the problem is occurring. Does that help? Look at the Hardware Interrupt/DPC usage. What would cause that to be so high?

enter image description here

And this pic is the same thing while the system is fine

enter image description here

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Can you post your resource monitor usage when its 99% ? is it possible to take a screenshot ? 99% System idle is normal – Andrew Keith Dec 14 '09 at 7:57
up vote 5 down vote accepted

a similar problem (high CPU usage caused by Deferred Procedure Calls) is being discussed here:

I am running Windows 7 Ultimate and my specs are AMD Phenom 9550 Quad-Core Processor 2.20 GHz with 6.00 GB RAM. The computer randomly spikes up to 80%+ and usually higher than that and the computer runs really slow. Ived tried checking for spyware, or anything and nothing is found. This happens at idle and during normal activity. Restarting usually solves the issue but sometimes it doesnt.

what seems to have solved the issue was this hotfix:

You encounter problems when you move data over USB from a Windows 7 or Windows Server 2008 R2-based computer that has an NVIDIA USB EHCI chipset and at least 4GB of RAM

Thanks alot! The hotfix did the job. I was so tired of 100% Usage... thats fixed now.

so, if your computer has an "NVIDIA USB Enhanced Host Controller Interface (EHCI) chipset" and "at least 4GB of RAM" and "you try to copy data from the computer to an external USB storage device" (i suppose, using a USB WLAN adapter qualifies for that too), then this might be the solution.

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Thanks, I tried this but it didn't show me anything new. The bottle neck was often "System Monitor" (it self) – Joe Dec 15 '09 at 7:05
edited my post, addressing your updates. – Molly7244 Dec 16 '09 at 18:26
I fit that description 100%. Can't wait to get home and try it :) thanks! – Joe Dec 16 '09 at 23:24
fingers crossed :) – Molly7244 Dec 16 '09 at 23:55
for 300 rep I would think they would be ;) I just installed it, so let's wait a day or so to see how things go :) – Joe Dec 17 '09 at 1:04

First, see if anything interesting is to be found in the Error Log.

You may use xperf whose use is described in Measuring DPC time. It's somewhat complicated to use, but can give you some answers.

Just a remark that in most cases the problem is hardware overheating. When the problem occurs, you might open the case and see if the RAM or GPU are too hot.

As far as tools go:
GPU-Z will tell you the temperature of the video card
SpeedFan for the CPU
Active@ Hard Disk Monitor for the hard disk

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Some "top of my head" culprits might be:

  1. "scheduled" (by W7, not you) fragmentation
  2. Indexing
  3. Like you mentioned, old or missing drivers. W7 is good at putting drivers in Windows Update > Optional Updates. If not I would get them from the manf website, starting with BIOS, Chipset, System Interface, and Video. Then go down the list from there.
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