What is causing my computer to slow down and how can I fix it?

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Discussion Overview

The discussion revolves around troubleshooting performance issues on a Windows XP notebook, specifically addressing unexpected slowdowns despite low reported CPU and RAM usage. Participants explore potential causes, including hardware interrupts, overheating, and driver issues related to hard drive modes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant notes that the task manager shows low resource usage while the fans are loud, suggesting a possible overheating issue.
  • Another participant suggests using "Process Explorer" to identify processes that may be consuming CPU resources.
  • A participant mentions experiencing high CPU usage due to Bluetooth drivers attempting to install devices, which may relate to the original issue.
  • Discussion includes the observation that "hardware interrupts" can consume significant CPU resources, raising questions about their expected behavior.
  • One participant identifies that their hard drive had switched from DMA to PIO mode, causing significant slowdowns, and shares their solution of deleting the driver to restore performance.
  • Another participant discusses a Windows feature that switches to PIO mode after drive errors, particularly affecting DVD playback, and suggests a method to revert to DMA mode.
  • There is a mention of differing experiences regarding the effectiveness of solutions to restore DMA mode, indicating variability in outcomes.

Areas of Agreement / Disagreement

Participants express various hypotheses regarding the causes of the slowdown, with some agreeing on the impact of hardware interrupts and driver modes, while others share differing experiences and solutions. The discussion remains unresolved regarding the best approach to address the underlying issues.

Contextual Notes

Limitations include potential dependencies on specific hardware configurations, variations in Windows XP behavior, and the lack of consensus on the most effective troubleshooting steps.

Who May Find This Useful

Users experiencing similar performance issues on Windows XP systems, particularly those with dual-core processors or related hardware configurations.

CRGreathouse
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I'm running Windows XP on a dual-core notebook and I noticed that sometimes (like now ;)) the computer slows down dramatically as though under heavy load, but the task manager reports nothing: the system idle process claims 97% of the CPU and there's only ~500 MB of RAM in use (on a 2 GB system). But the fans run loudly, and the task maanger does report (in a contradictory way) that CPU usage is about 55%.

Any thought? I do have "show processes from all users" checked.
 
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It is just a wild guess, but if the fans run, perhaps your notebook is overheated so it automagically slows down? I was never interested in details but some processors (especially those targeted at notebooks) have fancy solutions implemented to save on energy and to diminish chances of overheating.
 
The laptop does have automagic slowdown (Intel's SpeedStep), but it wasn't on at that time.

Process Explorer may have found the problem. For a decent chunk of time, maybe two minutes, there was 40-50% CPU use for "hardware interrupts". Should they really take that much juice?
 
On occasion, I have an issue with my setup in which the Bluetooth drivers are trying to install devices it detected [which I don't want it do]. This eats up my CPU time as it struggles to install these devices. So, I have to manually kill off the process. (If I allow it to finish, the install eventually fails... so I kill it off early.)

So, something like this might be an issue.
Is there a particular process that is using up the CPU? Process Explorer can help identify the process.
 
robphy said:
So, something like this might be an issue.
Is there a particular process that is using up the CPU? Process Explorer can help identify the process.

Process Explorer calls the process that I identified above "hardware interrupts".
 
CRGreathouse said:
Process Explorer calls the process that I identified above "hardware interrupts".

possibly useful discussions:
http://forum.sysinternals.com/forum_posts.asp?TID=2064
http://forum.sysinternals.com/forum_posts.asp?TID=7775
http://forums.tweakguides.com/showthread.php?t=3733
 
Last edited by a moderator:
Thanks, I'll look into that.
 
CRGreathouse said:
But the fans run loudly, and the task maanger does report (in a contradictory way) that CPU usage is about 55%.
Since you have two CPUs that likely means that one of the cores is running 100% running a single threaded job.
 
  • #10
MeJennifer said:
Since you have two CPUs that likely means that one of the cores is running 100% running a single threaded job.

Yes, certainly. That's why I mentioned that I was a running dual-core.
 
  • #11
robphy said:
http://forum.sysinternals.com/forum_posts.asp?TID=7775

That did it for me! Or at least found the problem, which I trust I can fix. My hard drive went from DMA to PIO mode, so every time I used the hard drive everything slowed down.

I'm playing with
HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\Scsi\Scsi Port 0\DMAEnabled
now; hopefully this works.
 
  • #12
OK, it's solved. I deleted the driver for the primary IDE and rebooted twice. Now the hard drive is back to DMA and the computer is running at least four times faster.

Thanks a lot, robphy!
 
  • #13
There is a 'feature' of windows from XP onwards, after a certain number of drive errors it automatically switches to PIO mode.
This is a problem with DVDs, if you play a badly scratched disk it assumes the errors are due to the drive and switches to PIO which is often too slow to play movies.

See http://sniptools.com/vault/getting-back-to-dma-mode-in-windows-xp to fix it.
 
Last edited by a moderator:
  • #14
Ouch, that's good to know - I noticed my dvd drive running rediculously slow a few months ago and found it in PIO mode. Gotta love MS! What they should do instead is slow down the rotation of the disk, try to read the area a few times at a lower speed, then decide it is a disk error.
 
  • #15
mgb_phys said:
There is a 'feature' of windows from XP onwards, after a certain number of drive errors it automatically switches to PIO mode.
This is a problem with DVDs, if you play a badly scratched disk it assumes the errors are due to the drive and switches to PIO which is often too slow to play movies.

See http://sniptools.com/vault/getting-back-to-dma-mode-in-windows-xp to fix it.

Yes, this is an intentional feature -- though I thought it started in Win2000, not XP. Regardless, I happened to try that set of steps (though I didn't read that page) and they failed for me. Only deleting the driver worked.
 
Last edited by a moderator:

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