# CPU at 100% - Why??!!??! **URL:** \ **Category:** Factual Questions\ **Created:** [September 28, 2010, 6:17pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373 "2010-09-28T18:17:00Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Fiddle\_Peghead](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddle_peghead/32/3506_2.png) [@Fiddle\_Peghead](https://boards.straightdope.com/u/Fiddle_Peghead)\ **Post date:** [September 28, 2010, 6:17pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/1 "2010-09-28T18:17:00Z")
I turn on my computer, bring up Firefox, and only Firefox, and my CPU usage immediately shoots up to 100%. It then varies from around 70% up to 100%. This is a Vista machine, bought in 2007. In Task Manager, Resource Monitor tells me that svchost.exe (netsvcs) Host Process for Windows Services has a value in the CPU column of 50. Nothing much else is going on. And now, because it knows I’m asking about it, this value just went down to zero and the problem has disappeared. But I am confident it will happen again. Any insight into this would be greatly appreciated, and of course let me know what other information you might need. Thanks! ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [September 28, 2010, 6:33pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/2 "2010-09-28T18:33:31Z")
depends on the version. it can take a minute to start and hogs the machine until it does. the structure and features of it have changed. the older the machine and OS the worse it is. ---
**Author:** ![Fiddle\_Peghead](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddle_peghead/32/3506_2.png) [@Fiddle\_Peghead](https://boards.straightdope.com/u/Fiddle_Peghead)\ **Post date:** [September 28, 2010, 6:39pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/3 "2010-09-28T18:39:04Z")
> [@johnpost](#): > > depends on the version. it can take a minute to start and hogs the machine until it does. the structure and features of it have changed. the older the machine and OS the worse it is. This goes on for 10, 20, 30 minutes sometimes, and of course it is now back. And I haven’t turned off the computer since my first post. Can anything be done about this? ---
**Author:** ![Amblydoper](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@Amblydoper](https://boards.straightdope.com/u/Amblydoper)\ **Post date:** [September 28, 2010, 6:55pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/4 "2010-09-28T18:55:14Z")
I’m not on a windows machine, but there is a way to see what services any given instance of SVChost.exe is running. You may need to install a third party app to do this. ---
**Author:** ![Fiddle\_Peghead](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddle_peghead/32/3506_2.png) [@Fiddle\_Peghead](https://boards.straightdope.com/u/Fiddle_Peghead)\ **Post date:** [September 28, 2010, 6:57pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/5 "2010-09-28T18:57:48Z")
> [@Amblydoper](#): > > I’m not on a windows machine, but there is a way to see what services any given instance of SVChost.exe is running. You may need to install a third party app to do this. Indeed there is. These are the services (Name, Description): AeLookupSvc - Application Experience; Appinfo - Application Information; BITS - Background Intelligent Transfer Service; I just looked again and realized there are many more services for this. They all have a PID of 1084. I don’t suppose this is significant… ---
**Author:** ![Captain\_Amazing](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@Captain\_Amazing](https://boards.straightdope.com/u/Captain_Amazing)\ **Post date:** [September 28, 2010, 7:05pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/6 "2010-09-28T19:05:01Z")
Do you have AVG antivirus running? It’s been known to take up all of the CPU resources. ---
**Author:** ![Fiddle\_Peghead](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddle_peghead/32/3506_2.png) [@Fiddle\_Peghead](https://boards.straightdope.com/u/Fiddle_Peghead)\ **Post date:** [September 28, 2010, 7:09pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/7 "2010-09-28T19:09:46Z")
> [@Captain\_Amazing](#): > > Do you have AVG antivirus running? It’s been known to take up all of the CPU resources. No. But thanks. ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [September 28, 2010, 7:13pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/8 "2010-09-28T19:13:42Z")
Have you installed any new add-ons recently? ---
**Author:** ![Fiddle\_Peghead](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddle_peghead/32/3506_2.png) [@Fiddle\_Peghead](https://boards.straightdope.com/u/Fiddle_Peghead)\ **Post date:** [September 28, 2010, 7:59pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/9 "2010-09-28T19:59:38Z")
> [@Tom\_Tildrum](#): > > Have you installed any new add-ons recently? No. And I just got back in after being gone an hour. It’s still going strong. ---
**Author:** ![Dangerosa](https://avatars.discourse-cdn.com/v4/letter/d/22d042/32.png) [@Dangerosa](https://boards.straightdope.com/u/Dangerosa)\ **Post date:** [September 28, 2010, 8:02pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/10 "2010-09-28T20:02:55Z")
iTunes? Or an iPod or iPhone plugged in? You can try process explorer. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [September 28, 2010, 8:06pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/11 "2010-09-28T20:06:56Z")
I got this a lot and I pinned it down to Windows Update. Switch off automatic updates and it might fix it. ---
**Author:** ![drachillix](https://avatars.discourse-cdn.com/v4/letter/d/48db29/32.png) [@drachillix](https://boards.straightdope.com/u/drachillix)\ **Post date:** [September 28, 2010, 8:21pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/12 "2010-09-28T20:21:55Z")
> [@Dangerosa](#): > > You can try process explorer. To elaborate > **[Process Explorer - Sysinternals](https://learn.microsoft.com/en-us/sysinternals/downloads/process-explorer)** > > Find out what files, registry keys and other objects processes have open, which DLLs they have loaded, and more. this will allow you to see what the services svchost tasks actually contain ---
**Author:** ![Al\_Bundy](https://avatars.discourse-cdn.com/v4/letter/a/e79b87/32.png) [@Al\_Bundy](https://boards.straightdope.com/u/Al_Bundy)\ **Post date:** [September 28, 2010, 9:54pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/13 "2010-09-28T21:54:57Z")
> [@Colophon](#): > > I got this a lot and I pinned it down to Windows Update. Switch off automatic updates and it might fix it. I was just about to say maybe there is something updating in background, but it should finish eventually. I also wonder if the machine is low on memory and if the hard drive has little space and is heavily fragmented. ---
**Author:** ![Superfluous\_Parentheses](https://avatars.discourse-cdn.com/v4/letter/s/8edcca/32.png) [@Superfluous\_Parentheses](https://boards.straightdope.com/u/Superfluous_Parentheses)\ **Post date:** [September 28, 2010, 10:20pm UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/14 "2010-09-28T22:20:57Z")
Hold on for a minute. /rolls cigarette. _lights_ _puffs_ A 100% cpu usage is generally good. It means whatever programs are running are doing it as fast as they can (excepting abuse or inefficient algorithms). That is; as long as it stops within some expected time limit. BUT, if you’re not expecting programs to do much of anything, it’s useful to find out what is going on. svhost.exe seems to be a program prone to obscuring the issue here. See [http://download.cnet.com/8301-2007\_4-9865052-12.html](http://download.cnet.com/8301-2007_4-9865052-12.html) ---
**Author:** ![Askance](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/askance/32/8281_2.png) [@Askance](https://boards.straightdope.com/u/Askance)\ **Post date:** [September 29, 2010, 12:30am UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/15 "2010-09-29T00:30:18Z")
[http://itknowledgeexchange.techtarget.com/itanswers/problem-with-high-cpu-usage-with-svchostexe/](http://itknowledgeexchange.techtarget.com/itanswers/problem-with-high-cpu-usage-with-svchostexe/) > [@](#): > > I have had this problem in the past and it was Windows update causing the issue, basically I turned of Automatic updates, and the update service. Next I manually updated and put the latest service pack on and all was ok again. ---
**Author:** ![arseNal](https://avatars.discourse-cdn.com/v4/letter/a/ecae2f/32.png) [@arseNal](https://boards.straightdope.com/u/arseNal)\ **Post date:** [September 29, 2010, 1:49am UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/16 "2010-09-29T01:49:39Z")
> [@Fiddle\_Peghead](#): > > > [@Amblydoper](#): > > > > I’m not on a windows machine, but there is a way to see what services any given instance of SVChost.exe is running. You may need to install a third party app to do this. > > Indeed there is. These are the services (Name, Description): AeLookupSvc - Application Experience; Appinfo - Application Information; BITS - Background Intelligent Transfer Service; > > I just looked again and realized there are many more services for this. They all have a PID of 1084. I don’t suppose this is significant… So, have you tried turning off any of these services? I would suspect BITS first. After that, windows update like someone else said. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [September 29, 2010, 2:13am UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/17 "2010-09-29T02:13:55Z")
> [@Superfluous\_Parentheses](#): > > Hold on for a minute. > > /rolls cigarette. _lights_ _puffs_ > > A 100% cpu usage is generally good. It means whatever programs are running are doing it as fast as they can (excepting abuse or inefficient algorithms). That is; as long as it stops within some expected time limit. That’s not quite accurate. If it’s at 100% and you are doing everything you need to be doing, and it’s all running smoothly, then that’s a good thing. However, that will only happen if the program is graceful, and will pause every few milliseconds to let other processes have a turn if they need it. I will however point out that Vista is set up to try and not waste processor cycles, and will actually do stuff when the computer is idle. Again, if you are not actually experiencing any slowdowns with your programs, then you are perfectly fine. I do wish it would limit itself below 100%, though. ---
**Author:** ![scm1001](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@scm1001](https://boards.straightdope.com/u/scm1001)\ **Post date:** [September 29, 2010, 2:52am UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/18 "2010-09-29T02:52:39Z")
Any other antivirus? - they tend to do lots of file searching in the background. Sophos was a problem on my vista machines - and it wouldnt show up on my Task manager. I had to go into Taskmanager/ performance tab/ resource monitor button /CPU tab to find that savservice.exe (sophos) was chewing up my CPU. However, if it is only firefox then some of these tips may help [Firefox CPU usage - MozillaZine Knowledge Base](http://kb.mozillazine.org/Firefox_CPU_usage) ---
**Author:** ![dzero](https://avatars.discourse-cdn.com/v4/letter/d/5f9b8f/32.png) [@dzero](https://boards.straightdope.com/u/dzero)\ **Post date:** [October 23, 2010, 6:40am UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/19 "2010-10-23T06:40:36Z")
I had a similar problem recently and when I looked into it via the performance monitor, the culprit seemed to be a javascript file called “sessionstore-1.js”. A little more research lead to [this enlightening thread on another site.](http://forums.mozillazine.org/viewtopic.php?f=38&t=1542035) It seems that the problem results from competition between firefox and various flavors of antivirus software. The quick and dirty fix is to type about:config into the address line, then type sessionstore into the search box. One of the entries will be browser.sessionstore.interval. This is measured in milliseconds and defaults to 10 seconds (10000 ms). Change that to something less annoying like 10 minutes and all will be well. Apparently you might lose some info during a crash of firefox, but I’ll gladly make that particular trade off. They give you more info at the link above so it’s worth looking at. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [October 23, 2010, 7:08am UTC](https://boards.straightdope.com/t/cpu-at-100-why/555373/20 "2010-10-23T07:08:46Z")
:smack: And I’ve had that problem before, dzero. Although I fixed it by putting the sessionstore files on an exception list in my AV. [Next page](https://boards.straightdope.com/t/cpu-at-100-why/555373.md?page=2)