Virtual PC vs. Power Management

Virtual PC vs. Power Management

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It seems that people are constantly running into problems running Virtual PC on laptop systems with advanced power management.  The reason for this is that Virtual PC is very demanding on hardware and has very strict timing requirements - and as each new revision of laptops comes along these systems perform more and more complex power management.

Problems start happening when these laptops tweak with things that we rely on.  This can either be caused when the laptop changes the CPU frequency too often, or when the laptop actually powers down sections of the system that we are dependant on in order to conserve power.  When this happens the user can see a variety of problems; ranging from sporadic pauses and bursts, virtual machines running too fast or too slow, repeated keystrokes or missing keystrokes to other timing related problems.

If you are seeing these problems you should:

  1. Install the laptop manufacturer’s power management tools.  Sometimes using these to change the power settings can resolve the problem (though not always).

  2. Check for any bios updates available for your laptop.  From time to time we work with laptop manufacturers to address issues we encounter as part of a BIOS update.

  3. If nothing else works - you can almost always solve these problems by installing Seti@home (or folding@home).  These programs use 100% CPU running at idle priority, which means that they do not affect any other programs running on your computer - but they effectively stop the laptop from performing any power management.


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  • Question:

    Would it help to create a custom power scheme using the powercfg command (XP SP2 or 2003 only)?

    This command lets you set the processor-throttle-ac and -dc to none.

    Any thoughts on this?
  • I was excited when I saw this post as I have been tormented by what I call the "CPU Blitz" since I first started using VP on my Dell Latitude D600. I downloaded and installed every driver I could find on I installed Windows XP SP2. In installed a patch I got from Microsoft support. I installed SpeedswitchXP. Nothing helped.

    After reading your post today, I installed seti@home and set it to work. Then I started three VMs planning to run a build in each VM, something that usually triggers the blitz. I never got that far as my CPU stepped down to 600 MHz before the third VM finished booting.

    This is driving me crazy! Do you have any suggestions?

  • Sorry. I should have asked if you have any more suggestions. I think that I have tried everything you suggested in your original post.

    Thank you,

  • An update:

    I suspended seti@home because since I installed it, my CPU steps down from 1.7GHz to 600MHz within 30 minutes after I boot. IOW, it has the opposite effect on my system that intended.

    When I can carve a day or two out of my schedule I plan to do a theraputic reinstall of Windows. I don't know what else to do.

  • Did you check for BIOS updates? IIRC, that solved some issues that were reported in the vpc newsgroup.
  • You can try RMClock:

    [quote]Dynamic on-demand clock modulation adjustment is supported on:
    Intel Pentium M/Celeron M, Intel Pentium 4/Celeron (all cores), Intel Xeon (all cores), Intel Pentium D/Pentium Extreme Edition featuring On-Demand Clock Modulation (ODCM).[/quote]
  • Yes, I installed the latest BIOS update.
  • I visited the RMClock site. I don't understand how it could be configured to prevent the CPU slowing down. Can you explain?


  • I installed RMClock. I confess that I don't have a clue about what most of the settings mean. It sounds like I need to read the Pentium M documentation in order to understand what to do and I think it would be way over my head.

    What I want is for my Pentium M CPU to *not* slow down randomly. I want to do that without damaging the CPU. I am definitely concerned that I could screw something up and damage my CPU.

    Can anyone advise me? I feel the same way about the settings in SpeedswitchXP.

    Thank you,

  • This is interesting - I perceived the problem to be the VPC processing too fast - for example, when I held down ALT-TAB, it flipped through applications at light speed. However, I am also experiencing the problem on a Dell D600 laptop intermittmently when the laptop is plugged into AC power and when running on batteries, so I will try changing some power management options - although I believe it already has the latest firmware as well as Dell PM drivers etc.
  • i have a question... i'm doing a win7 lab and am trying to install a captured image using WDS and it's saying my processor speed is only 2mhz and need at least 750 or so... this is an i7 system that has been manually set to 190bclk X19... so auto steping SHOULD be disabled right?? since i have it manually clocked... don't know how to get it to recognize that it has plenty of Processor... literally i have it at 3.6 on air and the most it uses is 6% with 3 VMs running... any ideas?

    don't know if i'll find this site again... please

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