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Windows 10 x64 intel system.

I've got a strange problem that, best I can tell, seems to be Task Manager balantly lying about CPU usage. Since today it will claim 100% CPU usage (128% in resource monitor) and attribute the 100% to fairly random processes that happen to be running--a game, video encode, whatever has the highest real CPU usage is given an insane % like 50% for reading an audio file.

The Performance tab showing basically 100% Kernal Times which must be the actual issue. Found several solutions about kernel time, ended up running Process Explorer looking for high system interrupts--nope, <1% CPU on interrupts, >90% CPU being used by SYstem Item Process.

The CPU is not actually running at 100%. The "details" tab of Task Manager also shows almost all CPU being used by System Idle process as normal. The CPU is quiet and cold so I can tell for sure it's not actually running at max. Programs open and run totally normally, including video games and video encoding. The CPU is acting completely normal other than Task Manager seemingly lying about the CPU usage.

Tried reboots, closing all apps and uninstalling recent hardware installations in device manager (a new Elgato HD60 pro capture card and a wireless 360 controller adapter I've used before).

What did work, concerningly, is a diagnostic startup, and a second startup with all NON-microsoft services/startup items enabled did not have the issue. Re-enabling all microsoft services in msconfig started showing the problem is. So the problem seems to be a service, a Microsoft one at that, but that's about all I can tell.

Upon one reboot I DID get 100% System Interrupts actually, and the PC was basically inoperable. Had to hard shut it down, now it's back to "normal", reporting but not actually at 100% CPU and fully usable.

  • What are the disk average response times looking like? especially on the system drive. I wonder if this isn't caused by I/O operations timing out/failing. – badp Oct 10 '15 at 23:04
  • Install the Win10 WPT (part of the Windows 10 SDK: dev.windows.com/en-us/downloads/windows-10-sdk) next time you see the CPU usage, capture a trace with xperf and share the compressed ETL file: pastebin.com/pgE11HRD – magicandre1981 Oct 11 '15 at 7:04
  • When different ways of measuring the same thing give different results, a prime suspect is an imperfect rootkit that is messing with certain processes. The more common programs are more likely to be lied to. Is it possible you got hit by malware? – Snowbody Jan 24 '17 at 13:39

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