In some scenario, you will need to upgrade the windows operating system RAM to more than 4GB. But, in normal circumstances, Windows 2000 (Datacenter Server or Advanced Server) or Windows 2003 server operating system, wont be able to use more than 4GB RAM event though more RAM modules have been installed. To enable
In 32-bit Windows operating system, there is one method to access memory above 4 GB and this method has been widely implemented which called Physical Address Extension (PAE). PAE is the added ability of the IA32 processor to address more than 4 GB of physical memory. The following operating systems can use PAE to take advantage of physical memory beyond 4 GB:
Microsoft supports Physical Address Extension (PAE) memory in Microsoft Windows 2000, Windows XP, and Windows Server 2003 products:
Operating system | Maximum memory support with PAE |
Windows 2000 Advanced Server | 8 GB of physical RAM |
Windows 2000 Datacenter Server | 32 GB of physical RAM |
Windows XP (all versions) | 4 GB of physical RAM* |
Windows Server 2003 (and SP1), Standard Edition | 4 GB of physical RAM* |
Windows Server 2003, Enterprise Edition | 32 GB of physical RAM |
Windows Server 2003, Datacenter Edition | 64 GB of physical RAM |
Windows Server 2003 SP1, Enterprise Edition | 64 GB of physical RAM |
Windows Server 2003 SP1, Datacenter Edition | 128 GB of physical RAM |
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
Resources
1. http://support.microsoft.com/kb/283037
2. http://problemandsolutions.blogspot.com
Dimitri Nek
Dimitri is a Linux-wielding geek from Newport Beach and a server optimization guru with over 20 years of experience taming web hosting beasts. Equipped with an arsenal of programming languages and an insatiable thirst for knowledge, Dimitri conquers website challenges and scales hosting mountains with unmatched expertise. His vast knowledge of industry-leading hosting providers allows him to make well-informed recommendations tailored to each client’s unique needs.
Windows 2003 Server 32-Bit [Datacenter Edition and Enterprise Edition] can support in excess of 4Gb memory but it is not enabled by default. To enable it, do the following:
- Open My Computer with Windows Explorer
- Ensure that you can see System and Hidden files:
- Click on Tools -> Folder Options
- Select the View tab
- Select the following
- Show hidden files and folders
- Uncheck Hide extensions for known file types
- Uncheck Hide protected operating system files (Recommended)
- Click OK
- Navigate to C:\
- Right-click on boot.ini and click on Properties
- Uncheck the Read-Only flag and click OK
- Open boot.ini in Notepad
- Change your boot.ini entries from something like this:
- Reboot the system.
[boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows Server 2003, Enterprise" /fastdetect /NoExecute=OptOut
to this (note the /PAE at the end):
[boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows Server 2003, Enterprise" /fastdetect /NoExecute=OptOut /PAE
You should now see any memory beyond 4Gb. The following maximum’s apply where PAE is enabled:
Version | Limit on x86 | Limit on X64 |
Windows Server 2003 R2 Datacenter Edition | 64GB | 1TB |
Windows Server 2003 R2 Enterprise Edition | 64GB | 1TB |
Windows Server 2003 R2 Standard Edition | 4GB | 32GB |
More info on the /PAE switch can be found here:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa366796%28v=vs.85%29.aspx
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 | Maximum memory support with PAE |
---|---|
Windows 2000 Advanced Server | 8 GB of physical RAM |
Windows 2000 Datacenter Server | 32 GB of physical RAM |
Windows XP (all versions) | 4 GB of physical RAM* |
Windows Server 2003 (and SP1), Standard Edition | 4 GB of physical RAM* |
Windows Server 2003, Enterprise Edition | 32 GB of physical RAM |
Windows Server 2003, Datacenter Edition | 64 GB of physical RAM |
Windows Server 2003 SP1, Enterprise Edition | 64 GB of physical RAM |
Windows Server 2003 SP1, Datacenter Edition | 128 GB of physical RAM |
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:
Code:
[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:
Code:
[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
how to add /PAE in windows 2008/win 7 ?
1. Click Start- All Programs-Accesories-Commando Prompt — «Right
Click-Run as administrator»
2. «Bcdedit /set PAE forceenable«
3. Restart Server
cheers!!!
Gaurang Patel
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Возникла давеча проблема — Windows 2003 Enterprise Server 32 bit не видит ОЗУ больше чем 3 ГБ. Решением может послужить добавление ключа PAE в файл boot.ini, после чего файл принимает приблизительно такой вид:
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WIND
Для справки:
Physical Address Extension (PAE) — режим работы встроенного блока управления памятью x86-совместимых процессоров, в котором используются 64-битные элементы таблиц страниц (из которых для адресации используются только 36 бит), c помощью которых процессор может адресовать 64Gb памяти (вместо 4Gb, адресуемых при использовании 32-разрядных таблиц). Также, в новых моделях процессоров в PAE-режиме старший бит элемента таблицы страниц отвечает за запрет исполнения кода в странице. Впервые расширение появилось в процессоре Pentium Pro. Для использования 36-разрядной адресации памяти необходима поддержка расширения физических адресов на уровне системной платы и включение режима PAE в ОС.