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I've got Win8.1, and an Intel CPU with 2(4) (logical) Cores.

BUT: Windows only uses 1 core. The Taskmanager shows the 1st CPU permanently at 100%; all others are mostly idle.

After several hours of search I only found out that windows sets the affinity of every process to CPU0. In the taskmanager I could reset the affinity of any process to any other CPU (or to all), but thats not necessarry on my other computer either.

Any other ideas than msconfig (heard that often on the internet, but it does not fix my problem. Windows knows about the other CPUs, they are just not used)?

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    are you saying that by default every process has affinity set to core0? the default really should be all cores...
    – Blaine
    Jan 28, 2017 at 14:33
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    I can confirm from observation that Windows does not by default set affinity of all processes to Core 0. All cores are used. If this is not happening, something is wrong. Other than the boot options I am not aware of any option that would restrict this.
    – LMiller7
    Jan 28, 2017 at 14:52
  • @Blaine yes, thats what i mean. i go to Taskmanager and check affinity of any process, only CPU0 is checked. I also know that this is not ok, this should not be normal, but it somehow is. I want to find out what is wrong and maybe fix without doing a whole reinstall...
    – Dániel Somogyi
    Jan 28, 2017 at 18:36

2 Answers 2

Reset to default
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Please read this link Psychic debugging

This Powershell (runas an administrator) script might help discovering which processes have affinity set.

get-process | Select Name,ProcessorAffinity

This script might at least temporyrily set the mask to all available (1+2+4+8) processors = 15 for a two-core processor with HT (a four-core with hyperthreading = 255)

get-process |
  Where{ $_.ProcessorAffinity -eq 1} |
    Foreach{ $_.ProcessorAffinity = 15 }
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  • Thanks for the link. Reading seems to exatly show my problem (but the links on the page do not work). I tried setting affinity of explorer to all CPUs (via Taskmgr) but windows does not save it (check all boxes -> hit ok -> recheck affinity: Still only CPU0). I will try powershell later today...
    – Dániel Somogyi
    Jan 30, 2017 at 9:29
  • Sorry for the delay, i tried powershell now. It does not completely work; select Name,ProcessorAffinity outputs exactly what expected; everything is set to 1. Running the Script AND the select as one script shows every process set to 15, but if I re-run the select most processes are resetted to 1 Exceptions are some svchost and DptfParticipantProcessorService... To the link: unfortunately the outgoing links on the site do not work...
    – Dániel Somogyi
    Feb 6, 2017 at 9:38
  • Sorry again, i messed up the line; The second process staying at 15 is dllhost, not the DptfParticipantProcessorService
    – Dániel Somogyi
    Feb 6, 2017 at 9:45
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I got it; Some of the pre-installed Intel-software throttled the CPU. Going to Programms and Features and deleting the Intel thermal plattform fixed and a restart fixed everything.

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