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Windows 7randomly goes into low power mode for many minutes. RRS feed

  • Question

  • I have an HP Elitebook 8540w (Intel i7) with 8GB of memory running Window7 64 bit. Some of my colleagues are suffering the same  problem but have  different HP laptops and oen has a Dell. Their laptops run different set of software as we have differing roles in the department. They are all work laptops and one has even been rebuilt by IT and it exhibited the same problem a few hours after being rebuilt. The company forces Windows updates onto the PC and Mcafee virus scanning.

    All of the laptops started to exhibit the same problem about 3-4 weeks ago and so is very unlikely to be a hardware problem.

    The first sign of it is that the the  laptop runs very slowly. For example it can take 5-15 seconds for characters to appear when typing and  2-3minutes to change  a window. Even if this is a window viewed a few seconds ago. This is not a virtual memory swap problem. This state typically occurs for between 5 & 40 minutes and then will rectify itself. On my laptop initially this was occurring once a day, but over the past week has started doing it 3 or more times aday.

    If one looks in Task Manager or Procexp the CPU will be running at near 100% with processes taking far more CPU processor percentage than normal. No one process dominates and they are different processes on the other laptops.  Even more interestingly the interrupts are typically 5-12%, far higher than normal. I ran DPC latency checker and it shows continual DPC latency times of ~16ms when the problem is occurring as opposed to the 200-2000us when the laptop is running OK. One of the other laptops has shown the same pattern using the DPC latency checker.

    I then analysed the driver times using Windows Performance Toolkit. This showed that the time inside the drivers (all drivers? I looked at ~ 20  ) was some 5-10 time longer than when it was working properly. My conclusion was that the CPU was running slowly, but why?

    Some Googling suggested power management. I used CPU-Z and i7 Turbo to look a the clock multiplier and C0state when it is going wrong and compare it to a good state.

    In simple terms:

    With normal  processes running the laptop in a good state the power management et al. show
    CPU 18% usage (system idle=82%), multiplier varying quite quickly between 12-18 across all CPUs, C0State averaginig 18% across all CPUs, Fan not running, fast  Core temperatures ~52C

    With 4 infinite loop  processes to force 100%CPU running but the laptop in a good state the power management et al. show
    CPU 100% usage, multiplier 22-22.45 across all CPUs, C0State 99.8% across all CPUs, Fan running fast  Core temperatures ~79C

    With normal  processes running but the laptop in a 'failed'  state the power management et al show
    CPU 100% usage, multiplier 9 across all CPUs, C0 state 16% across all CPUs, Fan not running, Core temperature <50C

    I came to the conclusion that something was forcing the laptop into a lower power state when it should not be. I tried using the the power management app available in Control Panel to set the minimum power level to 50% and 80% for both battery and mains power but to no effect.

    I have found other threads that are similar ( W7 Can't Stop CPU Throttling, Windows 7 Professional 64-bit freezes randomly et al. )but no recent threads that match the problem

    Given this is happening on multiple platforms, it seems to me that that it can only be the OS or related app or possibly a virus. IT have done all they can to eliminate viruses, so I come to the conclusion it is an OS issue.

    Some additional information.

    1) The cursor continues to respond well to mouse and touchpad movements.

    2) Getting into a console window can take a long time, but once into the console window the command line responds immediately. Any program that you execute may take a long time to execute.

    Please does any one know a solution or can help to diagnose the problem further?

    many thanks

    David Chilvers


    • Edited by DavidCh32 Sunday, April 21, 2013 4:18 PM
    Saturday, April 20, 2013 9:05 PM

Answers

  • Hi David,

    To eliminate application’s conflicts, you could try Clean Boot:

    http://support.microsoft.com/kb/929135

    Beyond that, please use command to restore the power plans to default settings, follow these steps:

    1. Click Start;

    2. In the search programs and files box, type cmd;

    3. Right click cmd, and then click Run as administrator;

    4. At the command prompt, type powercfg –restoredefaultschemes, and the press Enter;

    5. At the command prompt, type exit to exit the Command Prompt windows;

    6. Restart the computer.

    Best regards,

    Karen Hu

    • Marked as answer by Cloud_TS Friday, April 26, 2013 5:14 AM
    Tuesday, April 23, 2013 6:23 AM

All replies

  • Hi David,

    To eliminate application’s conflicts, you could try Clean Boot:

    http://support.microsoft.com/kb/929135

    Beyond that, please use command to restore the power plans to default settings, follow these steps:

    1. Click Start;

    2. In the search programs and files box, type cmd;

    3. Right click cmd, and then click Run as administrator;

    4. At the command prompt, type powercfg –restoredefaultschemes, and the press Enter;

    5. At the command prompt, type exit to exit the Command Prompt windows;

    6. Restart the computer.

    Best regards,

    Karen Hu

    • Marked as answer by Cloud_TS Friday, April 26, 2013 5:14 AM
    Tuesday, April 23, 2013 6:23 AM
  • Hi Karen

    Thank you for your response.

    I had a repeat classic today and during the time it was failing I did the following using powercfg

    I queried the schemes with powercfg -L and noted that the current scheme was balanced. Using powercfg I checked the minimum and maximum power states and they were 20 & 100% respectively. Cooling was set to active on AC Power. These were as I had set in via the power options in the control panel.

    I then did 'powercfg -restoredefaultschemes'. This had no immediate effect. I rebooted and the lower power problem had disappeared, but this is not unusual.

    I queried the current scheme and noted that the minimum and maximum power states were 5 & 100% respectively.

    I now need to wait to see if the problem reoccurs. This may take a few days to be sure.

    Could you explain why running powercfg –restoredefaultschemes is any different to what I had been setting/checking in the control panel->Power Options?

    Thanks

    David Chilvers

    Tuesday, April 23, 2013 3:22 PM
  • Hi David,

    Thanks for your test. Please go on observing. If some situation occur let us known.

    Using that commands will overwrite all default schemes if the power plans become corrupted. the power option “ Restore default settings for this plan” of Control Panel is just for current plan, not all.

    Best regards,

    Karen Hu

    Wednesday, April 24, 2013 8:58 AM
  • I have not been using my laptop over the last 10 days so have not had much time to observe the problem.

    I had reset the power management and last week had another occurrence. Another suggestion was to reset the BIOS. However I am still getting the problem. So no further forward.

    Tuesday, May 7, 2013 9:47 AM