Go Back   TechArena Community > Technical Support > Computer Help > Windows Vista > Vista Help
Become a Member!
Forgot your username/password?
Tags Active Topics RSS Search Mark Forums Read

Sponsored Links

Vista: high (45-50%) CPU usage due to hardware interrupts

Vista Help

Thread Tools Search this Thread
Old 25-11-2008
Eric T
Posts: n/a
Vista: high (45-50%) CPU usage due to hardware interrupts

Like many other people, every now and again the CPU useage on my Vista
machine goes up to 45-50% (which is likely to be nearly 100% of one of the
CPU's cores). This doesn't show up in task manager's processes: all of those
percentages are very low. Thank God I have two cores, or I'd be totally up
the creek: the juddering delays are bad enough as it is.

I got hold of the Process Explorer and that
shows that it's almost entirely hardware interrupts. Maybe duff hardware or
a badly written driver? Still no luck in tracing the precise cause.

It would be great if Process Explorer or some Microsoft diagnostic actually
showed which interrupt/s were being generated so frequently, so that one
could then trace that to a particular driver or piece of hardware.

Reply With Quote
Old 25-11-2008
Join Date: Apr 2009
Location: Michigan
Posts: 1

if so, ill tell you what to do

No, it's not wireless, though I do have one USB to ethernet connector to my
network hub between machines and an ethernet card connected to a broadband

I use USB flash sticks but the problem seems independent of them.

Just found the Kernrate tool at:

This may help me track down the cause, though I'm not sure if it'll work
with Vista, nor how which switches to use to get it to output details that
show how many "hits" each process is using and the percentage of CPU.
Reply With Quote
Old 25-11-2008
Eric T
Posts: n/a
Re: Vista: high (45-50%) CPU usage due to hardware interrupts + kernrate

Ah, all you need to do at the command line is navigate to the folder and
enter "kernrate", but in Vista you need to run an elevated command prompt,
ie run as an administrator, or the thing terminates with an error message
about privileges.
Reply With Quote
Old 08-12-2008
Eric T
Posts: n/a
Re: Vista: high (45-50%) CPU usage due to hardware interrupts

At last I have some figures, using KERNRATE (command prompt run as admin).
First percentage is when we have loads of hardware interrupts, figure in
brackets is when the system is running as normal:

intelppm 54% (98%): Intel processor device driver
ntkrnlpa 29% (0%): NT kernal and system
hal 9% (0%): Windows Hardware Abstraction Layer
rtnicxp 3% (0%): Realtek driver for RTL8139/810X family fast ethernet
network card (connected to my broadband router)
igdkmd32 2% (0%): Intel graphics kernal mode driver
others 0% (0%)

0% means just a handful of events ('hits'), if any, in the 10 second
sampling period.

I waited for the interrupts, unplugged the ethernet link to the broadband
router: no change. Switched off the router: no change.

The issue goes away if I reboot and comes back maybe days later / hours
after startup
Reply With Quote
Old 09-12-2008
Eric T
Posts: n/a
Re: Vista: high (45-50%) CPU usage due to hardware interrupts

I was advised to
look at my page file size in 'Task manager' - 'Performance' and this showed
that the programs I had loaded (the first figure of the two, bottom right)
were taking up more memory than the physical RAM installed. So I'm upgrading
from 1 to 2 GigaBytes of RAM, as advised by the downloadable system scan at
http://crucial.com/ .
Reply With Quote
Old 16-12-2008
Eric T
Posts: n/a
Re: [Resolved] Vista: high (45-50%) CPU usage due to hardware interrupts

I checked the disk with Start -- Run -- perfmon /res, to find that
SearchIndexer.exe had loads of entries and files open. Googling
"SearchIndexer.exe", it turned out that it was named as the cause of high
cpu usage.

As a workaround, I went into Start -- Run -- services.msc and found the
Windows Search entry, changed it from 'Automatic' to 'Manual' and rebooted.
At the time of writing, this seems to have worked.

p.s. Prior to this, having iTunes, I went into control panel -- indexing
options and unticked index xml files and the search indexer started to
rebuild the index.
Reply With Quote
Old 16-12-2008
Steve Thackery
Posts: n/a
Re: [Resolved] Vista: high (45-50%) CPU usage due to hardware interrupts

Thanks for reporting back. Incidentally, MS claims that SearchIndexer runs
with the lowest priorities for I/O and CPU, so although it uses the
processor when you're not doing anything, Vista should stick it on the back
burner as soon as you need the CPU.

In theory, then, it shouldn't affect the responsiveness or user experience.

Personally, I love the facility to find any text string in any indexed file
in less than a second - I use it all the time. So I really like Vista's new
SearchIndexer and wouldn't dream of turning it off.

Furthermore, if you wait a few days it quietens right down anyway.
Reply With Quote
Old 16-03-2009
Posts: n/a
Re: Vista: high (45-50%) CPU usage due to hardware interrupts

I have a newly-purchased Dell laptop, running 64-bit Vista, with 4GB of
RAM. Right out of the box, I'm having the same problem as the original
poster, i.e., some time after startup, my CPU usage goes to about 40%,
even when idle. No processes show up as being responsible when using
the built-in task list, but running the downloadable Process Explorer
shows that all this CPU usage is due to hardware interrupts.

I also have tried turning off search/indexing, and any unnecessary
drivers (such as the facial recognition software that came
pre-installed). Although the original poster eventually concluded he
didn't have enough memory, I have plenty of memory, so that's not the

Dell support has been useless. Their reps are apparently trained that
high CPU usage can only be caused by spyware, and they can't handle the
idea that this problem happened out of the box, with only preinstalled
software, and they certainly don't understand the idea that it is caused
by hardware interrupts (they are only trained to use the task manager
tool built into Vista).

So I'm stumped, and very frustrated. How do I fix this?
Reply With Quote
Old 05-07-2009
Posts: n/a
Re: [Resolved] Vista: high (45-50%) CPU usage due to hardware interrupts

I was having the same problem AFTER a fresh install, narrowed it down to
Marvell 61xx RAID driver (which was the latest), just disabled the
device and back to normal, but really irritating!
Reply With Quote

  TechArena Community > Technical Support > Computer Help > Windows Vista > Vista Help
Tags: , , ,

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads for: "Vista: high (45-50%) CPU usage due to hardware interrupts"
Thread Thread Starter Forum Replies Last Post
Saffire Radeon HD 4350 is giving hardware interruption and high CPU usage Pandeyji Monitor & Video Cards 3 12-04-2011 08:05 PM
High CPU usage for hardware interrupts - NIC activation issue Ashish Goenkar XP Hardware 3 29-10-2009 02:01 AM
High CPU Usage but No High Program Usage other than Idle kyosang Windows XP Support 5 18-04-2007 03:56 PM
High Memory Usage in Vista JP Vista Help 3 04-04-2007 07:45 PM

All times are GMT +5.5. The time now is 08:18 AM.