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How do I Make Maximum Memory Available to ZEMAX?
- By Mark Nicholson
- Published 20 August 2008
- Frequently Asked Questions
- Unrated
Use the /3GB switch
Question: My computer has 4GB of RAM, but ZEMAX doesn't seem to use it all. Why?
32-bit versions of Windows can address up to 232 memory addresses, or 4GB of memory. By default, Windows splits this memory up so that 2 GB is available to applications, and 2 GB is available to the operating system. That means ZEMAX can only access half the memory in your machine.
By changing a variable in the boot configuration, you can make 3 GB available to applications, and 'only' 1 GB to Windows itself. The method used depends on the version of Windows:
Windows 2000 - XP
Set the /3GB switch in the boot.ini file. See here for details.
Vista
Use BCDEdit /Set IncreaseUserVa 3072 to set the 3GB switch. This is a command line tool, see here and here for details.
Note that this only applies to 32-bit versions of Windows. XP64 and Vista64 will both supply up to 4GB (minus an overhead) to the current 32-bit release of ZEMAX, assuming it is available.
Note also that ZEMAX support cannot help you diagnose boot-related problems on your computer.
32-bit versions of Windows can address up to 232 memory addresses, or 4GB of memory. By default, Windows splits this memory up so that 2 GB is available to applications, and 2 GB is available to the operating system. That means ZEMAX can only access half the memory in your machine.
By changing a variable in the boot configuration, you can make 3 GB available to applications, and 'only' 1 GB to Windows itself. The method used depends on the version of Windows:
Windows 2000 - XP
Set the /3GB switch in the boot.ini file. See here for details.
Vista
Use BCDEdit /Set IncreaseUserVa 3072 to set the 3GB switch. This is a command line tool, see here and here for details.
Note that this only applies to 32-bit versions of Windows. XP64 and Vista64 will both supply up to 4GB (minus an overhead) to the current 32-bit release of ZEMAX, assuming it is available.
Note also that ZEMAX support cannot help you diagnose boot-related problems on your computer.
