Intel Physical Address Extensions cause high CPU usage in Windows 2000

This article has been archived. It is offered "as is" and will no longer be updated.
Consider this scenario: You use Intel Physical Addressing Extensions (PAE) on a computer that is running Microsoft Windows 2000 Advanced Server and that has more than 4 gigabytes of RAM. When the computer is under a heavy input/output (I/O) load, 80 to 100 percent of the CPU resources are used. If you do not use PAE, and the CPU is under a heavy I/O load, only 20 to 30 percent of the CPU resources are used. You expect that performance would be better when you use PAE.
This problem may occur if the Scsiport.sys driver allocates memory as non-cached, instead of cached, when you use PAE.

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.


You must have Windows 2000 SP4 installed to apply this hotfix.

Restart requirement

You must restart your computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later) 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   --------------------------------------------------------------   09-Mar-2004  18:54  5.0.2195.6906      74,128  Scsiport.sys
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For additional information about PAE, click the following article numbers to view the articles in the Microsoft Knowledge Base:
268363 Intel Physical Addressing Extensions (PAE) in Windows 2000
283037 Large memory support is available in Windows 2000 and Windows Server 2003
For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
816915 New file naming schema for Microsoft Windows software update packages
824684 Description of the standard terminology that is used to describe Microsoft software updates
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.
/PAE, Boot.ini

Article ID: 838150 - Last Review: 10/26/2013 20:59:36 - Revision: 3.5

Microsoft Windows 2000 Advanced Server, Microsoft Windows 2000 Datacenter Server

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