Accessing more than 2.0 GB of memory on
Windows® XP®

By default, Version 5 processes on Windows can allocate up to 2.0GB of memory for storing data and code. The 4GB address space offered by the operating system is split in two areas of 2GB each: the first 2GB is for user mode, and the other 2GB isg reserved by the kernel. On Windows® XP®, it is possible to increase the default allocation capabilities up to 3.0GB (3GB for user mode, 1GB reserved for kernel). Such capability requires additional tunings in order to be effective:

• From an operating system standpoint
• From a Version 5 standpoint

• Windows® XP® Professional is required.
• A modification of boot.ini file is needed to activate this capability at the system level. The boot.ini switch /3GB needs to be added in order to make 3GB available for user mode applications. For example:
  [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="Microsoft Windows XP Professional 3GB" /fastdetect /3GB
  multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect

Choose your solution

Technical information

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The Version 5 main executable needs to be made "Large Address Space Aware" in order to effectively take advantage of 3GB of address space. In order to do so, one should:

• locate and make a backup copy of the main executable (say, for example, CNEXT.exe, generally found in
  C:\Program Files\Dassault Systemes\B10\intel_a\code\bin; the same pattern is applicable for DMU.exe or Delmia.exe)
• run imagecfg.exe on CNEXT.exe
  • in a command session, execute imagecfg.exe -l CNEXT.exe
  • output of above command should be similar to:
    CNEXT.exe contains the following configuration information:
    Subsystem Version of 4.0
    Stack Reserve Size: 0x100000
    Stack Commit Size: 0x1000
    CNEXT.exe updated with the following configuration information:
    CNEXT.exe contains the following configuration information:
    Subsystem Version of 4.0
    Image can handle large (>2GB) addresses
    Stack Reserve Size: 0x100000
    Stack Commit Size: 0x1000
  • imagecfg.exe utility can be found on the Windows® 2000 Server Resource Kit Supplement One, or from \support\debug\i386 folder of a Windows® NT 4.0 CD-ROM.
• Customers having access to Microsoft® Visual Studio® 6 development environment can use editbin.exe as an alternative to imagecfg.exe. Using editbin.exe utility, generally found in C:\Program Files\Microsoft Visual Studio\VC98\bin, the syntax is as follows:
  editbin.exe /LARGEADDRESSAWARE CNEXT.exe

One can go back to initial behavior by restoring the original copy of CNEXT.exe (or original copy of main executable modified) and removing /3GB switch from the boot.ini file.

Some drivers may not load correctly when /3GB switch is added to boot.ini. In such case, one would need to apply Service Pack 1 on Windows XP, and tune /3GB configurations with /USERVA switch in boot.ini file. Please refer to Driver May Not Be Loaded with the /3GB Switch for more details.