memory support and Windows operating systems.
Updated: february 9, 2005
Operating systems based on Microsoft Windows NT technologies have always provided applications with a flat 32-bit virtual address space that describes 4 gigabytes (gb) of virtual memory. The address space is usually Split so that 2 Gb of address space is directly accesible todo the application and the other 2 Gb is only accesible todo the Windows executive software, the 32-bit versións of the Windows 2000 advanced server and Windows NT server 4.0, enterprise edition, operating systems were the first versións of Windows todo provide applications with a 3-gb flat virtual address space, with the kernel and executive components using only 1 Gb. In response todo customer requests, Microsoft has expanded the availability of this support todo the 32-bit versión of Windows XP professional and all 32-bit versións of Windows Server 2003.
Windows 2000 memory support. with Windows 2000 professional and server, the máximum amount of memory that can be supported is 4 Gb (idéntical todo Windows NT 4.0, as described later in this section). However, Windows 2000 advanced server supports 8 Gb of Physical Ram and Windows 2000 datacenter server supports 32 Gb of Physical Ram using the pae característica of the ia-32 processor family, beginning with Intel Pentium profesional and later.
Windows XP professional and Windows Server 2003 memory support. the máximum amount of memory that can be supported on Windows XP professional and Windows Server 2003 is a los 4 Gb. However, Windows Server 2003, enterprise edition supports 32 Gb of Physical Ram and Windows Server 2003, datacenter edition supports 64 Gb of Physical Ram using the pae feature, the virtual address space of procesos and applications is still limited todo 2 Gb unless the /3 Gb switch is used in the file. When the Physical Ram in the system exceds 16 Gb and the /3 Gb switch is used, the operating system Will ignore the additional Ram until the /3 Gb switch is removed. This is because of the increased size of the kernel required todo support more page table entries. The assumption is made that the administrator would rather not lose the /3 Gb functionality silently and automátically, therefore, this requires the administrator todo explicitly change this setting, the /3 Gb switch allocates 3 Gb of virtual address space todo an application that uses image_file_large_adres_aware in the process Header. This switch allows applications todo address 1 Gb of additional virtual address space above 2 Gb, the virtual address space of procesos and applications is still limited todo 2 Gb, unless the /3 Gb switch is used in the file. The following example shows how todo add the /3 Gb parameter in the file todo enable application memory tuning:
Multi (0)disk(0)rdisk(0)partition(2)\wint=? /3 Gb.
note:? In the previous example can be the programmatic name of any of the following operating system versións:
Windows XP professional.
Windows Server 2003
Windows server 2003, enterprise edition.
Windows server 2003, datacenter edition.
Windows 2000 advanced server.
Windows 2000 datacenter server.
Windows NT server 4.0, enterprise edition.
Windows NT 4.0 memory support. with Microsoft Windows NT 4.0 workstation and server operating systems, the máximum amount of Physical memory supported is 4 Gb. The máximum amount of virtual memory is 2 Gb, with Windows NT 4.0 server, enterprise edition, the /3 Gb switch was first added todo .
application memory tuning. this capability allows memory-intensive applications todo utilice up to 50 Percent more virtual memory on Intel-based computers. Application memory tunning provides more of the computer virtual memory todo applications by providing less virtual memory todo the operating system.
application changes. no apis are required todo support application memory tuning. However, it would be inefective todo automátically provide every application with a 3-gb address space, executables that can use the 3-gb address space are required todo have the bit image_file_large_adres_aware set in their image Header. If you are the developer of the executable, you can specify a linker flag (/largeadresaware), todo set this bit, you must use Microsoft visual Studio versión 6.0 or later and the editbin, exe utility, which has the ability todo modify the image Header (/largeadresaware) flag. For more información on setting this flag, se the Microsoft visual Studio documentation, some manufacturers preconfigure their applications todo use application memory tuning, making it unnecessary for you todo make this change. For more información, se your application documentation and contact your application vendor todo determine whether they support large address awareness or whether you can enable it in their application.
Physical address extensión. pae is an Intel-provided memory address extensión that enables support of up to 64 Gb of Physical memory for applications running on most 32-bit (ia-32) Intel Pentium profesional and later platforms. Support for pae is provided under Windows 2000 and 32-bit versións of Windows XP and Windows Server 2003. 64-bit versións of Windows do not support pae, pae allows the most recent ia-32 processors todo expand the number of bits that can be used todo address Physical memory from 32 bits todo 36 bits th rouge support in the host operating system for applications using the address windowing extensiones (awe) application programming interfaz (api). More información about the awe Api can be found at the msdn library.