Not All Physical Memory May Be Reported By The Operating System

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Article ID: 555458 - View products that this article applies to.
Author: Yuval Sinay MVP
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SUMMARY

The following knowledgebase will help you resolve a problem when not all of the physical memory is recognized when you install your server with 4 GB RAM.

SYMPTOMS

When exactly 4 GB of memory is installed on certain servers hardware running Microsoft Windows 2000/Server 2003, operating system utilities such
as WinMSD or System Properties may report a memory value that is approximately 512 MB less than the total system memory that is actually installed.

CAUSE

This behavior occurs because the Intel E7520 chipset or AMD Opteron 8000 chipset used on these servers includes PCI Express serial
I/O technology which requires a certain amount of memory.
The PCI devices use up additional memory, which is then unavailable to be used by the operating system
With PCI Express, there is a 256 MB block of memory allocated to the PCI Extended Configuration space, no matter how many devices are installed in the system.
In addition, the PCI cards will use an additional 256 MB of space for their PCI memory regions; therefore, 512 MB of physical memory will typically be unavailable.

RESOLUTION

 
Option A:
 
1. Upgrade the current drivers and BIOS/Firmware to the latest version.
 
Note: It is recommended to contact your hardware vendor support before applying changes to the current system.
 
2. Consider enabling the "PAE" mode.
 
     Physical Address Extension - PAE Memory and Windows
 
     http://www.microsoft.com/whdc/system/platform/server/PAE/PAEdrv.mspx
 
Note: Enable "PAE" mode can decrease applications performance. Its recommended to
            check the changes impact on test machine before applying it to production server.
 
 
Option B:
 
1. Upgrade the current drivers and BIOS/Firmware to the latest version.
 
Note: It is recommended to contact your hardware vendor support before applying changes to the current system.
 
2. Upgrade the server memory to more then 4.5 GB RAM.
 
 

MORE INFORMATION

 
Intel Physical Addressing Extensions (PAE) in Windows 2000
 
http://support.microsoft.com/default.aspx?scid=kb;en-us;268363&sd=tech
 
Large memory support is available in Windows Server 2003 and in Windows 2000
 
http://support.microsoft.com/default.aspx?scid=kb;en-us;283037
 

Properties

Article ID: 555458 - Last Review: September 20, 2005 - Revision: 1.0
APPLIES TO
  • Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
  • Microsoft Windows Small Business Server 2003 Standard Edition
  • Microsoft Windows Small Business Server 2003 Premium Edition
  • Microsoft Small Business Server 2000 Standard Edition
  • Microsoft Windows 2000 Enterprise Edition
  • Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
  • Microsoft Windows Server 2003, Standard Edition (32-bit x86)
Keywords: 
kbpubmvp kbpubtypecca kbhowto KB555458
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