Enable PAE in x86 32-bit Windows Server 2003 and 2000 to Use Large 4GB or More RAM Memory

[Johnny]

After installing Windows 2000 (Datacenter Server or Advanced Server) or Windows 2003, system properties shows that only around 3.37 GB of physical memory (RAM) is available for application and system use, although 4 GB or more RAM modules have been installed, and BIOS can correctly identifies the full installed size of physical memory, which means that the motherboard and x86 or x64 CPU processor can support more than 4 GB of physical memory.

32-bit Windows operating system depends on PAE (Physical Address Extension) feature to use more than 4 GB of physical memory. On most Windows 2000 and Windows Server 2003 system, especially those run in NUMA mode on a NUMA-capable computer. PAE is disabled by default. PAE is enabled by default only if DEP (Data Protection Execution) is enabled on a computer that supports hardware-enabled DEP, or if the computer is configured for hot-add memory devices in memory ranges beyond 4 GB.

Thus, if PAE is not enabled in Windows 2000 and Windows Server 2003 (for example, if DEP is turned off by administrator), the system may not able to detect, identify and see more than 4GB memory, and will have to allocate slightly more than 3GB of memory for system and application only as some memory address space has to be reserved and mapped for system devices and peripherals.

To enable PAE in Windows Server 2003 and Windows 2000 (and Windows XP), append the /PAE switch to the end of the line of operating system in the Boot.ini file. To disable PAE, use the /NOPAE switch. The Boot.ini normally located in the root folder (i.e. C:\) with Read-Only and Hidden attributes, which are required to be removed before the file can be edited.

For example,

Original Boot.ini:

[boot loader]
timeout=0
default=multi(0)disk(0)rdisk(0)partition(1)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINNT=”Microsoft Windows 2000 Advanced Server”
/fastdetect

Change the Boot.ini to become:

[boot loader]
timeout=0
default=multi(0)disk(0)rdisk(0)partition(1)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINNT=”Microsoft Windows 2000 Advanced Server”
/fastdetect /PAE

For Bootcfg command, use:

bootcfg /raw "/pae" /A /ID 1

Restart the computer after modification to make the change effective.

Note that even with PAE enabled, there is still memory limit imposed by the operating system itself. The table below list the maximum memory support with PAE enabled for Windows 2000, Windows Server 2003 and Windows XP. Most 32-bit client based Windows operating system, such as Windows XP and Windows Vista (see way to use large memory of more than 4GB in 32-bit Windows Vista), has OS level limit that restricts the maximum amount of memory able to be used to 4GB.


Operating system : Windows 2000 Advanced Server
Maximum memory support with PAE : 8 GB of physical RAM

Operating system : Windows 2000 Datacenter Server
Maximum memory support with PAE : 32 GB of physical RAM

Operating system : Windows XP (all versions)
Maximum memory support with PAE : 4 GB of physical RAM*

Operating system : Windows Server 2003 (and SP1), Standard Edition
Maximum memory support with PAE : 4 GB of physical RAM*

Operating system : Windows Server 2003, Enterprise Edition
Maximum memory support with PAE : 32 GB of physical RAM

Operating system : Windows Server 2003, Datacenter Edition
Maximum memory support with PAE : 64 GB of physical RAM

Operating system : Windows Server 2003 SP1, Enterprise Edition
Maximum memory support with PAE : 64 GB of physical RAM

Operating system : Windows Server 2003 SP1, Datacenter Edition
Maximum memory support with PAE : 128 GB of physical RAM

[Kooldinesh]

Not a standard edition of Win2k3.

[PeterAGASSI]

Windows Server 2003 can support upto more than 4GB with PAE enabled.

[msshahanshah]

So just want to confirm If I do enable PAE on my windows server 2003 standard edition can I add more than 6gb of physical memory and have the OS detect it correctly. Or do I have to upgrade to enterprise edition ?

[EINSTEIN_007]

Originally Posted by msshahanshah

So just want to confirm If I do enable PAE on my windows server 2003 standard edition can I add more than 6gb of physical memory and have the OS detect it correctly. Or do I have to upgrade to enterprise edition ?

If you are running a system that has 4 GB of RAM installed and you then add 4 GB of additional RAM on Windows Server 2003, Windows may recognize only 4 GB of physical memory or possibly 6 GB 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 are similar to the symptoms that occur when you do not add the /PAE switch to the Boot.ini file.

[Scooby67]

Is there a processor impact when enabling PAE? I want to allow for more memory usage but I don't want to impact performance in the process.

(Windows Server 2003, Standard Edition SP2)

[HiSpeed]

In Windows Server 2003, PAE is automatically enabled only if the server is using hot-add memory devices. In this case, you do not have to use the /PAE switch on a system that is configured to use hot-add memory devices. In all other cases, you must use the /PAE switch in the Boot.ini file to take advantage of memory over 4GB. Typically, a process running under Windows 2000 or Windows Server 2003 can access up to 2 GB of memory address space (assuming the /3GB switch was not used) with some of the memory being physical memory and some being virtual memory. The more programs (and, therefore, more processes) that run, the more memory you commit up to the full 2 GB of address space.

PAE Processor Usage

[pclarke]

I have server 2003 standard 32 bit. I have added 32 gig of memory to the server. I have enable /PAE. How can the server recognize the full memory. I have turned off redundant memory as well.

[Itronix]

Hello while searching about your query i found the following query. just go through it. i am sure that you will get the all helpful solution on it.
http://support.microsoft.com/kb/283037