2 GB limit

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The 2 GB limit refers to a physical memory barrier for a process running on a 32-bit operating system, which can only use a maximum of 2 GB of memory.[1] The problem mainly affects 32-bit versions of operating systems like Microsoft Windows and Linux, although some variants of the latter can overcome this barrier.[citation needed] It is also found in servers like FTP servers or embedded systems like Xbox.[citation needed] The use of Physical Address Extension (PAE) can help overcome this barrier.[clarification needed]

While Linux, FreeBSD, and most Unix-Likes support PAE so long as the hardware does[2][3], Windows needs this boot option enabled manually. This is known as 4-gigabyte tuning (4GT), or the /3GB switch. Once enabled, executables can have the "large address aware" flag set to increase their memory limit to 3GB. 32-bit processes on 64-bit Windows are also limited to 2GB. However, they can use the "large address aware" flag as well, except that it doesn't require the /3GB switch and increases the limit to 4GB.[4]

It could also refer to the maximum partition size for the FAT16 file system in versions of Windows prior to XP.[5]


  1. ^ Richardson, Mike (24 July 2014). "Overcoming the Windows 2GB Caching Limit". O'Reilly Media. Retrieved 2015-08-18.
  2. ^ "2.3.23-pre4 x86 64 GB RAM changes [HIGHMEM patch] explained a bit". 10 October 1999. Retrieved 2017-09-17.
  3. ^ "Chapter 4. Hardware Compatibility". Retrieved 2017-09-17.
  4. ^ "Memory Limits for Windows and Windows Server Releases". Microsoft. Retrieved 2017-09-17.
  5. ^ "Maximum partition size using the FAT16 file system in Windows XP". Microsoft. Retrieved 2015-08-18.

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