The engineers responsible for Intel's Core Duo processor and Centrino Duo platform are a bit frustrated.  Years of hard work leading up to the platform's launch in early January was first plagued by the problem of availability.  Core Duo and Centrino Duo notebooks are still not widely available, and that will continue to be the case at least for another week or two.  Outside of availability, another even more troubling problem crept up - could it be that the Core Duo platform had a bug that significantly reduced battery life when paired with any USB 2.0 device?  The folks at Tom's Hardware originally uncovered the issue, when they noted that battery life on their ASUS Core Duo notebook dropped dramatically after merely connecting an external USB 2.0 device. 

How much more frustrating could things get?  After spending years of work on a new mobile CPU and platform, your customers still really can't buy them and the one thing that everyone remembers about them is that they have some sort of a bug that reduces battery life.  When you've spent a good deal of your design time trying to increase battery life, having a reputation of decreasing it before notebooks are widely available has to be a tough pill to swallow. 

However, the case isn't as open and shut as that; the original test data indicated that this was primarily a Core Duo problem, while Microsoft insists that the problem should affect all notebooks.  The other issue is that, until last week, every single Core Duo platform that we could get our hands on was pre-production.  There's also the question of whether or not the problem is caused by the actual USB device used.  And finally, amongst all of this debate and finger pointing, a temporary solution actually existed, just begging to be tested. 

We set out on investigating this issue immediately after it was discovered, but soon found out that it was a lot more complicated than we thought upon first glance.  We've spent almost the past two weeks performing non-stop battery life testing on five notebooks with up to 4 different USB devices, testing theories, trying to pinpoint exactly what causes this problem and testing Microsoft's fix.  What follows is the process that we went through in our labs when faced with this strange bug.

Starting at the Beginning
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  • Eris23007 - Monday, February 13, 2006 - link

    P.S. That's why you read more than just the intro and conclusion pages before asking questions.

  • DigitalFreak - Monday, February 13, 2006 - link

  • Eris23007 - Monday, February 13, 2006 - link

    The USB hard drive they tested with had its own power supply. The "USB Drive" was a flash device (USB bus powered), while the "External HDD" was:


    Vantec NexStar 2 External 3.5" Hard Drive Enclosure (USB 2.0)

    Note that this device is entirely externally powered

  • UNCjigga - Monday, February 13, 2006 - link

    I will have to do some testing on my notebook with the 'workaround' fix installed. I could have sworn that around the time I installed SP2 on my lappy the battery life suffered, but this was about 6-12 months after I got it so I just figured the battery was getting old.
  • Ionizer86 - Monday, February 13, 2006 - link

    Wow, this is getting interesting. I'm surprised that this bug affects 915 based systems too. I wonder if this could be a broader issue that may affect intel 855 systems or AMD-based computers with chipsets from other vendors. I suppose I could do some playing around
  • Ionizer86 - Monday, February 13, 2006 - link

    No edit button... (accidental post before completion).
    I could test this out on my 855 based laptop if only I had Perfmon and the special plugin :)
  • Ionizer86 - Tuesday, February 14, 2006 - link

    Specs: Thinkpad R50e, Pentium M 1.5 on i855GME.

    I booted into Windows normal mode as cleanly as possible and ran Perfmon. The CPU was usually in C2 ~60% of the time and C3 ~35% of the time, for a total of ~95% in C2 or C3. Upon plugging in any of my USB stuff (an external hard disk, a Sandisk Cruzer mini, or even my IBM mouse), I'd get 95% in C2 and 0% in C3. Maybe my mouse is a USB 2.0 mouse; not sure.

    Battery draw goes from about 11.7W to 12.5W when I plug in my mouse.

    By adding the registry key, I no longer have the issue with the Cruzer or my external hard disk, but the problem with the mouse remains.

    Looks like MSFT has quite a problem at hand.
  • Accord99 - Tuesday, February 14, 2006 - link

    0.8W, maybe its the power draw of the mouse itself?
  • johnsonx - Monday, February 13, 2006 - link

    Adding to what Jason said, you only need the 'secret' plugin for Core Duo processors. The C3 state counter that Perfmon already has works fine on older platforms.
  • IntelUser2000 - Tuesday, February 14, 2006 - link


    Adding to what Jason said, you only need the 'secret' plugin for Core Duo processors. The C3 state counter that Perfmon already has works fine on older platforms.

    Not just Core Duo, but: "As you can probably guess, Perfmon is inaccurate in this case. While Perfmon does a fine job of monitoring C3 states for older processors, it fails to handle properly the CPUs we're most interested in: the Pentium M and Core Duo."

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