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I am facing this weird problem with my Windows 7 Dell laptop (Core i5, 8 GB ram). The problem starts when every time I disconnect the power cable and use the laptop in battery for a while (lets say half an hour) then reconnect the power cable.

After connecting the power cable back suddenly every process become CPU hungry and all of them tries to take as much CPU as they can, no matter what they are doing! Even the task manager takes about 17-20% percent CPU!

If I kill some process/application to free up CPU use, some other process take up the free CPU, so the CPU use remain in constant 100% use. Only way out for me is to restart the Windows. I am wondering the reason of this kind of weird behavior, Is there anyone faces something similar to this? Is there any idea how to track down the reason?

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I'm going to throw out the possibility the CPU is being throttled (multiplier reduced) for some reason, which means less processing power available, which makes each process take a higher "percentage". I have no idea what might be causing throttling though. –  Bob Mar 31 '12 at 14:38
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Programs such as CPU-Z (64-bit standalone executable) can display your current CPU multiplier, try comparing before and after plugging in. Keep in mind, for power saving purposes, it is normal for the multiplier to be lower than the max when there is nothing intensive running. For example, my laptop's i5 can go up to 23x but sits at 8x when idle. The max would be the default clock rate divided by the "Bus Speed" CPU-Z shows. –  Bob Mar 31 '12 at 14:44
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It seem that you are right, my CPU is being throttled! At the beginning core-speed was about 2926 MHz and multiplier was around 22, then after disconnecting the power core-speed falls back to 2261 Mhz and multiplier count remain around 16, but after reconnecting the power cable at first core-speed and multiplier values goes up but then they start to fall continuously! At the moment when I am typing this the code-speed is only 931Mhz and Multiplier count is only 7 :(. Is w7 responsible for this? –  sowrov Mar 31 '12 at 15:27
    
Are your drivers up to date, especially mother board drivers? –  Tom Wijsman Mar 31 '12 at 16:35
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1 Answer

This is normal behavior.

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Change that to active such that it increased fan speed instead, the downside is more battery usage.

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After connecting the power cable back suddenly every process become CPU hungry and all of them tries to take as much CPU as they can, no matter what they are doing! Battery usage should not be an issue here. It is possible Plugged in was set to Passive though. –  Bob Mar 31 '12 at 16:04
    
@Bob: Well, in any case the above settings control that. So he needs to verify they are set correctly first... –  Tom Wijsman Mar 31 '12 at 16:05
    
@Tom: In my power plan (to fix this issue) I set 100% cpu use for all Plugged in cases and 'Active' in both cases as well. But the problem remains unsolved :( –  sowrov Mar 31 '12 at 16:17
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@sowrov: No, the minimum needs to be as low as possible, the maximum needs to be as high as possible. Above how mine are configured (by default) and yours should be very similar... –  Tom Wijsman Mar 31 '12 at 16:35
    
I think this problem is rare defect of Dell-lat 6400 I am trying to use this application, hoping it will fix the issue, Lets see what it can do... :-? –  sowrov Apr 2 '12 at 7:48
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