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.
The problem mainly affects
32-bit
In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...
versions of
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
s like
Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
and
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...
, although some variants of the latter can overcome this barrier. It is also found in servers like
FTP servers or embedded systems like
Xbox
Xbox is a video gaming brand created and owned by Microsoft. The brand consists of five video game consoles, as well as applications (games), streaming services, an online service by the name of Xbox network, and the development arm by the na ...
.
The use of Physical Address Extension (
PAE) can help overcome this barrier.
While Linux,
FreeBSD
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...
, and most
Unix-like
A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
operating systems support PAE so long as the hardware does,
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 3 GB. 32-bit processes on
64-bit Windows are also limited to 2 GB. 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 4 GB.
See also
*
640 KB barrier
In DOS memory management, conventional memory, also called base memory, is the first 640 kilobytes of the memory on IBM PC or compatible systems. It is the read-write memory directly addressable by the processor for use by the operating system ...
*
3 GB barrier
In computing, the term 3 GB barrier refers to a limitation of some 32-bit operating systems running on x86 microprocessors. It prevents the operating systems from using all of 4 GiB () of main memory. The exact barrier varies by motherboar ...
References
Computer files
Computer file systems
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