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You may experience memory performance issues on a Windows 2000-based computer that has multiple Intel Pentium 4 processors

This article has been archived. It is offered "as is" and will no longer be updated.
For a Microsoft Windows Server 2003 version of this article, see 897335.
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 Description of the Microsoft Windows registry
On a Microsoft Windows 2000-based computer that has multiple Intel Pentium 4 processors, you may experience the following symptoms:
  • An unexpectedly slow startup time.
  • Memory performance issues.
  • CPU spikes in the system process that occur immediately after startup.
This problem may occur if the page zeroing thread is configured to use the extended memory manager interface (XMMI) instruction set.

When a process allocates virtual memory, the Windows memory manager will clear the virtual memory pages before the memory manager lets the requesting process access the pages. This step makes sure that a process cannot access data in virtual memory that was previously owned by another process.

The page zeroing thread that is responsible for cleaning used memory pages is configured to use one of two instruction sets early in the startup process. By default, the page zeroing thread is configured not to use the XMMI instruction set on Pentium 4 multiprocessor systems. This restriction exists because of hardware issues that cause a decrease in performance on many Pentium 4 multiprocessor systems. Under certain conditions, the XMMI instruction set is incorrectly selected. This issue may be more common on single processor virtual machines that run on multiprocessor hosts. A virtual machine may incorrectly select the zeroing loop because the virtual machine detects a single processor during startup on a multiprocessor host.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To install this hotfix, you must be running Windows 2000 Service Pack 3 or Windows 2000 Service Pack 4. (SP4) For more information, click the following article number to view the article in the Microsoft Knowledge Base:
260910 How to obtain the latest Windows 2000 service pack

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix replaces the hotfix that was originally includedwith Windows 2000 SP4.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
     Date         Time    Version          Size        File name      --------------------------------------------------------------     10-Feb-2004  19:47   5.0.2195.6897      30,160    Mountmgr.sys      05-Apr-2004  20:39   5.0.2195.6921   1,700,928    Ntkrnlmp.exe      05-Apr-2004  20:39   5.0.2195.6921   1,700,608    Ntkrnlpa.exe      05-Apr-2004  20:39   5.0.2195.6921   1,722,176    Ntkrpamp.exe      05-Apr-2004  20:39   5.0.2195.6921   1,677,824    Ntoskrnl.exe  
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.

After you apply this hotfix, you must add and configure the XMMIZeroingEnable registry entry to disable XMMI-zeroing functionality. To do this, follow these steps:
  1. Click Start, click Run, type regedit in the Open box, and then click OK..
  2. Locate the following registry subkey:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\kernel
  3. In the left pane, right-click kernel, point to New, and then click DWORD Value.
  4. Type XMMIZeroingEnable as the entry name, and then press ENTER.
  5. Right-click XMMIZeroingEnable, and then click Modify.
  6. To disable XMMI-zeroing, type 2in the Value data box, and then click OK.

    Note To re-enable XMMI-zeroing, type 1 in the Value data box, and then click OK.
  7. Quit Registry Editor.
  8. Restart the computer.
The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Identyfikator artykułu: 816488 — ostatni przegląd: 10/26/2013 18:24:24 — zmiana: 6.7

Microsoft Windows 2000 Advanced Server, Microsoft Windows 2000 Professional Edition, Microsoft Windows 2000 Server

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