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I have scanned with avast a few times for virus's but nothing has been found, however.. every time i leave my computer for about 5 minutes the process labelled 'system' which is the 'ntoskrnl.exe' bumps the CPU of the entire machine up to 20-24% which of course spins the fans up high..

The strangest bit, once I press a key or move mouse the machine recognises i am back and system drops off to next to nothing.. I have googled it but cannot see anything that matches this scenario so thought I would ask on here.

enter image description here

After reading through a link (Troubleshoot High CPU usage by the "System" process) from a commenter who has since removed their comment i arrived at..

This link (ntoskrnl.exe!_misaligned_access eats a lot of CPU when idle) which I then found the item within system ramping up cpu is ntoskrnl.exe_misaligned_access+0x3f0

The guys reply in the above thread is to kill processes that end up there.. but I'm not sure if that is wise?

So i turned off the scheduled idle task and this has not made any difference, i just went away to get a coffee, returned to the sound of heavy fan use and cpu up to 20%.. the culprit in task manager, "system"

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John
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    the first two things I'd check are you virus scanner and Windows Update. They often try to operate when the user is idle. – Frank Thomas Aug 18 '15 at 17:11
  • Agree with @FrankThomas, those and file indexing, and tasks with an "on idle" trigger. – Ƭᴇcʜιᴇ007 Aug 18 '15 at 17:18
  • I extended the OP after reading through the post from DavidPostill i think i found the culprit.. – John Aug 18 '15 at 17:21
  • have you read my answer? Stop/disable the maintenance tasks and your issue is fixed. Windows does Memory scans – magicandre1981 Aug 18 '15 at 19:43
  • Strange. My comment appeared twice so I deleted one of them (not both). Anyway for the record is was take a look at [Troubleshoot High CPU usage by the "System" process](http://superuser.com/q/527401) – DavidPostill Aug 18 '15 at 20:42
  • Hi @magicandre1981 yes, this is the answer i was led to once i had narrowed down what was in the "system" process.. ie ntoskrnl.exe!_misaligned_access. I have disabled the Idle Maintenance as you suggested, it did not remedy the issue yesterday but i will keep an eye on it today i see if it helps. – John Aug 19 '15 at 08:38
  • @magicandre1981 turning off the idle schedule has not made any diff – John Aug 19 '15 at 10:19
  • also capture a xperf trace like the user in the other topic, – magicandre1981 Aug 19 '15 at 15:34

2 Answers2

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So it seems, touch wood, that i have finally fixed the issue.

After not getting anywhere with trying to chase down the system process being kicked off when in idle, i decided to install the latest updates.. wooo bad idea..

Down came this incredibly annoying windows 10 reminder. It reminded me about its presence 24/7 with it's logo in my task bar.

After reading a lot of tech posts on how crazy windows is getting with harvesting your data (must be turning in a marketing company :) probably something a little more invading but hey.. that's the world of free stuff right?

Anyway, i stumbled upon this blog post: https://www.hackread.com/microsoft-updates-spy-on-windows7-8-users/

Which bascially says, get rid of these updates:

    KB3075249    !important one
    KB3080149    !important one
    KB2923545
    KB2970228
    KB3035583
    KB2990214
    KB3021917
    KB3068708
    KB2592687
    KB2660075
    KB2506928
    KB2952664
    KB3050265
    KB2726535
    KB2994023
    KB3022345
    KB3022345
    KB2545698
    KB3065987

Find with 1 - run cmd 2 - start power shell 3 - run this command replacing with the rel. code:

get-hotfix -id KB3075249

For each one you find and decide don't want, uninstall with: 1 - run cmd (2nd instance to enable you to keep powershell running) 2 - run this command to remove:

wusa /uninstall /kb:2923545

And guess what.. after removing all the updates mentioned.. my laptops fans no longer go mental when i leave the room for 5 minutes! I wonder what the f**k windows was doing?

Vomit IT - Chunky Mess Style
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John
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    Windows does some checking about compatibility with Windows 10 and that causes some usage in the machine. Probably that's what was happening here. – Sami Kuhmonen Aug 26 '15 at 18:36
  • maybe.. kind of unbelievable that a software house as big as ms does something like that though. Hardly seems a big step to monitor itself on high cpu usage.. eitherway i am not convinced that is all that was going on there. Not after everything i have read so far. – John Aug 26 '15 at 19:47
  • Not all you read is true, though. But on my machine they were running compatibility tests at least. – Sami Kuhmonen Aug 26 '15 at 19:50
  • I think it even mentioned something to that effect in the release notes of at least one of those updates. If they're only using it for the sake of compatibility, then I'm glad, since mine is a homebrew system and I don't have the benefit of a manufacturer testing my system for Windows 10 compatibility. – GuitarPicker Aug 27 '15 at 13:32
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Without more information, its hard to say the cause. However, there are both Windows and 3rd party processes that wait till the computer is inactive to run. They do this in order to give the active foreground applications the most horsepower and not to slow down the computer when someone is using it. Processes like defraggers, AV, backups, etc. often wait for inactivity as they can noticeably slow down a system.

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