Thread: How much RAM can XP actually use?

Someone assumed 2GB is the most it will make use of. Is that exact?

Intel Core i7 920 Nehalem Quad @ 4.2GHz
EVGA GTX260 216 710/2500MHz
OCZ Platinum CL7 6GB
EVGA Intel X58

Do you suggest how much it can really make use of or how much can it identify? I consider that it can make out up to about 2.8GB. At least in 32-bit mode.

Operating systems support on Microsoft Windows NT technologies has always offered programs with a smooth 32-bit virtual address space that give details 4 gigabytes (GB) of virtual memory. The address space is generally crack so that 2 GB of address space is openly accessible to the application as well as the other 2 GB is only available to the Windows executive software.

The 32-bit versions of the Windows 2000 Advanced Server as well as Windows NT Server 4.0, Enterprise Edition, operating systems were the first versions of Windows to offer applications with a 3-GB flat virtual address space, with the kernel along with executive components by means of just 1 GB. In reply to customer requests, Microsoft has extended the accessibility of this sustain to the 32-bit version of Windows XP Professional as well as all 32-bit versions of Windows Server 2003.

Windows 2000 Memory Support. With Windows 2000 Professional and Server, the maximum amount of memory that can be supported is 4 GB (equal to Windows NT 4.0, as explained later on in this section). But, Windows 2000 Advanced Server supports 8 GB of physical RAM along with Windows 2000 Datacenter Server supports 32 GB of physical RAM by means of the PAE feature of the IA-32 processor family, opening with Intel Pentium Pro moreover afterward.

Windows XP Professional and Windows Server 2003 Memory Support. The utmost amount of memory that can be supported on Windows XP Professional as well as Windows Server 2003 is also 4 GB. But, Windows Server 2003, Enterprise Edition supports 32 GB of physical RAM as well as Windows Server 2003; Datacenter Edition supports 64 GB of physical RAM by means of the PAE feature.

The virtual address space of processes along with applications is still inadequate to 2 GB except the /3GB switch is used in the Boot.ini file. When the physical RAM in the system go beyond 16 GB and the /3GB switch is used, the operating system will disregard the extra RAM until the /3GB switch is detached. This is because of the enlarged size of the kernel necessary to support more Page Table Entries. The statement is made that the administrator would somewhat not misplace the /3GB functionality mutely as well as automatically; therefore, this requires the administrator to openly modify this setting.

The /3GB switch allocates 3 GB of virtual address space to an application that uses IMAGE_FILE_LARGE_ADDRESS_AWARE in the process header. This switch allows applications to address 1 GB of additional virtual address space above 2 GB.

The virtual address space of processes as well as applications is still restricted to 2 GB, except the /3GB switch is used in the Boot.ini file. The subsequent example shows how to attach the /3GB parameter in the Boot.ini file to allow application memory tuning:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINNT="????" /3GB

Note: "????" in the earlier example can be the programmatic name of any of the subsequent operating system versions:

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 utmost total of physical memory supported is 4 GB. The highest amount of virtual memory is 2 GB.

With Windows NT 4.0 Server, Enterprise Edition, the /3GB switch was first added to Boot.ini.

Application Memory Tuning. This ability permits memory-intensive applications to make use of up to 50 percent more virtual memory on Intel-based computers. Application memory tuning offers more of the PC virtual memory to applications by providing fewer virtual memories to the OS.

Application Changes. No APIs are necessary to sustain application memory tuning. But, it would be useless to automatically give every application with a 3-GB address space.

Executables that can utilize the 3-GB address space are necessary to have the bit IMAGE_FILE_LARGE_ADDRESS_AWARE set in their icon title. If you be the developer of the executable, you can state a linker flag (/LARGEADDRESSAWARE).

To place this bit, you have to make use of Microsoft Visual Studio Version 6.0 or later as well as the Editbin.exe utility, which has the capability to adjust the image header (/LARGEADDRESSAWARE), flag. For more details on setting this flag, see the Microsoft Visual Studio documentation.

Some producer preconfigures their applications to make use of application memory tuning, making it avoidable for you to make this alteration. For more information, observe your application documentation as well as call your application vendor to find out whether they support Large Address Awareness or whether you can allow it in their application.

PAE. Physical Address Extension is an Intel-provided memory address addition that allows support of up to 64 GB of physical memory for applications functioning on most 32-bit (IA-32) Intel Pentium Pro as well as later platforms. Support for PAE is offered below Windows 2000 as well as 32-bit versions of Windows XP along with Windows Server 2003. 64-bit versions of Windows do not support PAE.

PAE agree to the latest IA-32 processors to enlarge the number of bits that can be used to address physical memory from 32 bits to 36 bits through support in the host operating system for applications by means of the Address Windowing Extensions (AWE) application programming interface (API). More details about the AWE API can be established at the MSDN Library.