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I have a quad core laptop with win7. Around 3 months ago the laptop occasionally slowed down.

Resource Monitor and Process Explorer show that processor 0 was 100% busy with DCP and Interrupts. A restart temporarily has helped, but the problem returns.

(I rarely turn of the machine, I just close the lid and let it hibernate.)

At first I though this might be something with the IO, a disk fail or similar.

As another superuser question suggested I downloaded DPC Latency checker, and I indeed had a big latency. As suggested, I disabled drivers one by one, and found the problem: my Atheros ethernet card.

I tried downloading newer drivers, but they are up to date, so I just disabled it for good. I am using WiFi anyways. I opened up process explorer, and to my surprise, the processor was still at full use. So I had to take a different approach.

I have downloaded before the windows performance tools. After running xperf -on Latency I have found that ACPI.sys was taking 15.77 % of duration compared to the rest which was lower than 0.1%. I tried disabling ACPI-Compilant-Control Method Battery but it has not helped. Is it safe to disable other devices such as management interface for ACPI? I have no idea what this might be.

EDIT: It seems that there is a high chance to trigger this when i plug the computer in power. As one post suggested, when i put the computer to sleep, the high usage goes away again.

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A high DPC latency might not be the cause, but an additional result of the problem. That would explain why disabling the Atheros Ethernet does not solve the problem, you merely removed one symptom. For the real solution you will need to discover what is triggering all these interrupts. Is there anything in the log files? (Check with start, run, eventvwr.msc). Additional questions: How long does it take fort the problem to occur? Does it ever happen before your laptop uses hibernate or sleep modes? Does it happen if you boot another OS (live CD, to check software vs HW problems), ... –  Hennes Mar 21 '13 at 22:21
use xperf to trace the cause: msfn.org/board/index.php?showtopic=140263 Use the stackwalk option, I offered to see the callstack in the CPU Sampling Graph. –  magicandre1981 Mar 22 '13 at 5:38
what about ACPI.sys? how is this not an issue? –  Bartlomiej Lewandowski Mar 22 '13 at 9:38

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