Windows Vista or Windows Server 2003 may report less memory than you expect

Windows Vista or Windows Server 2003 may report less memory than you expect

Article ID : 929580
Last Review : February 14, 2008
Revision : 4.0
On This Page

SYMPTOMS

On a computer that has 4 gigabytes (GB) of random access memory (RAM), the System Properties dialog box and the System Information dialog box may report less memory than you expect.

This problem occurs in Windows Vista and in Windows Server 2003.

Important Windows Vista Service Pack 1 (SP1) made changes to the way components of the user interface (UI) report memory. For example, some components of the Windows Vista SP1 UI will now report when there is 4 GB or more of total physical memory that is installed on the computer. For more information about how memory is reported in Windows Vista Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:

946003 (/Feedback.aspx?kbNumber=946003/) Windows Vista Service Pack 1 will report 4 GB of system memory (RAM) on systems that have 4 GB of memory installed

Back to the top

CAUSE

This problem occurs because the address space is limited to 4 GB in a 32-bit hardware environment. Memory may be relocated to make room for addresses that the basic input/output system (BIOS) reserves for hardware. However, because of this limitation, Windows Server 2003 and Windows Vista cannot access memory that is relocated above the 4 GB boundary.

Back to the top

STATUS

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

Back to the top

MORE INFORMATION

A 32-bit operating system can address memory that is relocated above the 4 GB boundary if the following conditions are true:

• The computer is in Physical Address Extension (PAE) mode.
• The computer has 4 GB of RAM.

In this case, the operating system correctly reports how much memory is installed.

Additionally, some x64-based operating systems can address up to 2 terabytes (TB) of RAM. For more information, visit the following Microsoft Web page:

http://technet.microsoft.com/en-us/windowsserver/bb294403.aspx (http://technet.microsoft.com/en-us/windowsserver/bb294403.aspx)

To enable PAE mode, you have to add PAE to the boot entry in the BCD file. Open an elevated command prompt. Type BCDEDIT /SET PAE ForceEnable.

Note There is no Boot.ini file in Windows Vista. The Boot.ini file is used for legacy Windows versions when dual-booting only

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

268230 (/Feedback.aspx?kbNumber=268230/)Scaling out versus scaling up with Intel Physical Addressing Extensions (PAE)
283037 (/Feedback.aspx?kbNumber=283037/) Large memory support is available in Windows Server 2003 and in Windows 2000

If you add more memory to the system, the BIOS might recognize all the physical RAM even though Windows recognizes only a part of the RAM. If the computer uses a redundant memory feature or a memory mirroring feature, the full complement of memory may be invisible to Windows. Redundant memory provides the system with a failover memory bank when a memory bank fails. Memory mirroring splits the memory banks into a mirrored set. You can enable or disable these features by using the BIOS. You cannot enable or disable these features by using Windows. To modify the settings for these features, refer to the computer’s user manual or to the BIOS manufacturer’s Web site. Or, contact the manufacturer.

For example, if the computer has 4 GB of RAM installed, and you add 4 GB of additional RAM, Windows may recognize only 4 or 6 GB of RAM instead of the full 8 GB. The redundant memory feature or the memory mirroring feature may be enabled on the new memory banks without your knowledge. These symptoms resemble the symptoms that occur when you do not add the /PAE switch to the Boot.ini file.

Back to the top

Memory limits

For more information about the memory limits for Windows operating systems, visit the following Microsoft Web site:

http://msdn2.microsoft.com/en-us/library/aa366778.aspx (http://msdn2.microsoft.com/en-us/library/aa366778.aspx)

For more information about Physical Address Extensions (PAE), visit the following Microsoft Web site:

http://msdn2.microsoft.com/en-us/library/aa366796.aspx (http://msdn2.microsoft.com/en-us/library/aa366796.aspx)

For more information about memory addressing, see the following Microsoft Web log (blog):

http://blogs.msdn.com/oldnewthing/archive/2006/08/14/699521.aspx (http://blogs.msdn.com/oldnewthing/archive/2006/08/14/699521.aspx)

Back to the top


APPLIES TO
• Windows Vista Business
• Windows Vista Enterprise
• Windows Vista Home Basic
• Windows Vista Home Premium
• Windows Vista Starter
• Windows Vista Ultimate
• Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
• Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
• Microsoft Windows Server 2003, Standard Edition (32-bit x86)

Back to the top

Keywords: 
kbtshoot kbprb kbexpertiseinter KB929580

Back to the top

 

Microsoft Knowledge Base Article

This article contents is Microsoft Copyrighted material.
Microsoft Corporation. All rights reserved. Terms of Use | Trademarks


You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

AddThis Social Bookmark Button

Leave a Reply

*
To prove that you're not a bot, enter this code
Anti-Spam Image

Additional Articles From "Commerce Server 2007"