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Intel Core Duo USB Issue: A Mischaracterized Bug

by Anand Lal Shimpi on February 13, 2006 1:40 PM EST
61 Comments | Add A Comment
61 Comments
The Fix

The Microsoft Knowledge Base article that references the USB power drain problem also provides a solution to the problem, a simple registry edit that prevents the USB devices from keeping the processor from moving to lower power states.  The entire text of the KB article was actually anonymously posted in a Slashdot thread, and thus, is now publicly available.  As with any changes to your Windows Registry, be sure to hang onto a backup copy and make any modifications at your own risk:
A Windows XP SP2-based portable computer uses its battery power more quickly than you expect when a USB 2.0 device is connected

View products that this article applies to.

Partner Only Article Article ID : 899179

Last Review : July 12, 2005

Revision : 1.0

Important: This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 (https://premier.microsoft.com/kb/256986/) Description of the Microsoft Windows registry


SYMPTOMS

Consider the following scenario. You install Microsoft Windows XP Service Pack 2 (SP2) on a portable computer. Then, you connect a USB 2.0 device to the computer. In this scenario, the computer uses its battery power more quickly than you expect.

CAUSE

Windows XP SP2 installs a USB 2.0 driver that initializes any connected USB device. However, the USB 2.0 driver leaves the asynchronous scheduler component continuously running. This problem causes continuous instances of memory access that prevent the computer from entering the deeper Advanced Configuration and Power Interface (ACPI) processor idle sleep states. These processor idle sleep states are also known as C states. For example, these include the C3 and C4 states. These sleep states are designed, in part, to save battery power. If an otherwise idle portable computer cannot enter or maintain the processor idle sleep states, the computer uses its battery power more quickly than you expect.

RESOLUTION

Warning: Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk. To resolve this problem, add the EnIdleEndpointSupport entry to the USB registry key. To do this, follow these steps:
  1. Click Start, click Run, type regedit, and then click OK.
  2. Locate, and then click the following registry subkey:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\USB

    Note: If the USB subkey does not exist, create it. To do this, follow these steps:
    a. Select the Services key. On the Edit menu, point to New, and then click Key.
    b. Type USB in the New Key #1 box to name the new key "USB."

  3. Right-click USB, point to New, and then click DWORD Value.
  4. In the New Value #1 box that appears, type EnIdleEndpointSupport, and then press ENTER.
  5. Right-click EnIdleEndpointSupport, and then click Modify.
  6. In the Value data box, type 1, leave the Hexadecimal option selected, and then click OK.
  7. Quit Registry Editor.
STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

APPLIES TO

  Microsoft Windows XP Service Pack 2, when used with:

  • Microsoft Windows XP Professional
  • Microsoft Windows XP Home Edition
Unfortunately, the solution isn't completely ready for public deployment, as there are apparently still some scenarios where it doesn't fix the problem.  There may be issues with the problem re-appearing after putting your system to sleep, which are presently being worked on.  However, for the majority of situations, this simple registry modification should, in theory, take care of things.  With the solution in hand, and five notebooks to play with, we went to work.

Starting at the Beginning The Notebooks and the USB Devices
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  • lazybum131 - Tuesday, February 14, 2006 - link

    Actually, if you take into account the larger capacity battery on the T60, 56WHr compared 51 WHr, the T43 comes out ahead most of the time. The T60 has a 9.8% larger capacity battery, but with the fix it only comes out ahead 3.2%, 1.85%, 8.24% and 5.04%.

  • Anand Lal Shimpi - Monday, February 13, 2006 - link

    I'm looking into this issue myself and I will have an updated Core Duo performance article in the coming weeks that will address this as well as many other items. I wouldn't use the ASUS notebooks to compare Napa to Sonoma, especially given the internal USB 2.0 camera. I am hoping to do a Lenovo based Napa vs. Sonoma comparison that will hopefully make things a lot clearer.

    Take care,
    Anand

  • JarredWalton - Monday, February 13, 2006 - link

    I think that Napa allows a lower power setting, but you have to remember that two cores are still going to use more power than a single core when active. It might be interesting to see a test comparing Sonoma and Napa with the same CPU, as Dothan and Yonah both fix socket 479. There's also a question of the other peripherals, though: NIC, sound, screen, etc. all draw power. The newer Napa laptop from ASUS might have a better (re: brighter but more power hungry) LCD, for example, or a different HDD model. I don't know if they're strictly "identical" in other components, but a change of platform often involves other tweaks as well.

  • NullSubroutine - Monday, February 13, 2006 - link

    Id be more apt to say that the increase of the FSB and the second additional core are more likely the cause, because I think they did make sure the Asus laptops were exactly the same.

  • IntelUser2000 - Tuesday, February 14, 2006 - link

    quote:
    Id be more apt to say that the increase of the FSB and the second additional core are more likely the cause, because I think they did make sure the Asus laptops were exactly the same.


    Keep in mind that with laptops especially with power consumption there is so many variations to battery life problem. It could be that the implementation of the BIOS or voltage regulator is different across the two. Voltage regulator is said to be 5-10% of total power consumption, so differences in V-reg can make differences you are seeing.

    Look here: http://www.hardwarezone.com/articles/view.php?id=1...">http://www.hardwarezone.com/articles/view.php?id=1...

    Even with a faster CPU, MSI M635 with 1.8GHz Turion outperforms HP Compaq nx6125 with 2.0GHz Turion. It also gets better battery life even with X700.

    I think 5% difference is well within the range.

  • huges84 - Monday, February 13, 2006 - link

    Doh! I completely forgot about the dual vs single core issue. And your other points are valid as well.

  • kmmatney - Monday, February 13, 2006 - link

    Looks like I'll be using my old USB 1.1 mouse when I travel from now on.

  • huges84 - Monday, February 13, 2006 - link

    Yeah, a lot of people will be checking what version of USB their mouses are. I know I will be.

  • Saist - Monday, February 13, 2006 - link

    In reguards to THG, I was surprised to see a link as well.

    In reguards to AMD systems, I have a Turion on hand from Fujitsu (Lifebook S2000) and have been unable to duplicate the power loss from a default state with either a USB 2.0 external DVD drive, or a USB 2.0 Plextore ConvertX device.

    I was also surprised to see that Anandtech didn't test any Turion systems themsevles in the article. But, having tested 2 Centrino systems of my own (one from Sager, the other from Dell), in addition to the Fujitsu, yes, it is time consuming.

  • Zebo - Monday, February 13, 2006 - link

    Anand refuses to test new turions similarly equiped.. don't know why I've emailed him never heard back. Go to laptop logic.
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