Why does my System Process use 50% of CPU time?

Question

The System process running on my Windows 7 installation uses almost 50% of CPU arbitrarily. I monitor the process with Process Explorer from Sysinternals.

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What could be the problem?

Solution

In my situation it was cpu fan speed that was somehow slower than usual.

For some reason or another, the fan was slow, after 5 years of perfect operation, its settings got corrupt or whatever. So cpu got hot, so system was protecting things with this "high cpu usage in system process" trick. That is a trick to reduce core temperature.

In process explorer, system was ~40%, interrupts were 5-10%, dpc's were 5-10%.

These were some suggested solutions.

• restored the system, it did not help.
• scanned for viruses, nothing.
• re-installed graphics driver, nothing.
• plugged out all usb devices to see if they were doing this, nothing.
• deleted the pio entries in device manager > ide/ ata/atapi controllers, nothing.

All these with ample restarts.

The solution was, turning the fan full on, instead of the automatic speed change. Possibly something went wrong with the automatic fan speed settings.

Bios > somehow reach fan and cpu temperature related sections > check cpu temperature.

If 90C, you have it. The fan speed was 1500rpm, which was slower than what I could remember, 2500rpm. Also, there was no fan noise, normally I would hear a lot of fan noise if the cpu was hot. In the related section of bios, turn the fan full on, and save bios settings. Fan should turn on full after restart of bios. And process explorer should again show 100% idle :)

Hope this helps.

Comments

[Tamara Wijsman]

Please try this procedure and report back in the comments section.

[Admin]

I see you are running Kaspersky, it's happening to me similar to you with the same .... DPC item @ between 40% - 60% usually 50%. I'm running Norton BTW & it's a rare occurrence but I have to shut down & restart to clear it out I've left it run all day before but it never resolves the issue & keeps running @ 50%.

[Daniel R Hicks]

I had a problem with my laptop where the CPU would shoot to 50% and stay there, due apparently to an "open" interrupt that occurs when the WiFi radio is powered off.

[Johan]

No fan > cpu gets hot > core protection comes in (cpu frequency is reduced to reduce power consumption) > you suddenly have a 1/10 fast cpu > such a slow cpu is easily driven full 100% capacity by usual system tasks > system on win machines usually occupies only 1 core > you get 50% constant cpu use