IA-32 (short for "Intel Architecture, 32-bit", commonly called ''i386'') is the

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 a maximum of 32- bit units. Compared to smaller bit widths, 32-bit computers can perform la ...

version of the

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...

instruction set architecture In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, ...

, designed by

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

and first implemented in the

80386 The Intel 386, originally released as the 80386 and later renamed i386, is the third-generation x86 architecture microprocessor from Intel. It was the first 32-bit processor in the line, making it a significant evolution in the x86 architect ...

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

in 1985. IA-32 is the first incarnation of x86 that supports 32-bit computing; as a result, the "IA-32" term may be used as a

metonym Metonymy () is a figure of speech in which a concept is referred to by the name of something associated with that thing or concept. For example, the word "wikt:suit, suit" may refer to a person from groups commonly wearing business attire, such ...

to refer to all x86 versions that support 32-bit computing. Within various

programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...

directives, IA-32 is still sometimes referred to as the "i386" architecture. In some other contexts, certain iterations of the IA-32 ISA are sometimes labelled ''i486'', ''i586'' and ''i686'', referring to the instruction

superset In mathematics, a set ''A'' is a subset of a set ''B'' if all elements of ''A'' are also elements of ''B''; ''B'' is then a superset of ''A''. It is possible for ''A'' and ''B'' to be equal; if they are unequal, then ''A'' is a proper subset ...

s offered by the 80486, the P5 and the P6 microarchitectures respectively. These updates offered numerous additions alongside the base IA-32 set including floating-point capabilities and the MMX extensions. Intel was historically the largest manufacturer of IA-32 processors, with the second biggest supplier having been

AMD Advanced Micro Devices, Inc. (AMD) is an American multinational corporation and technology company headquartered in Santa Clara, California and maintains significant operations in Austin, Texas. AMD is a hardware and fabless company that de ...

. During the 1990s, VIA,

Transmeta Transmeta Corporation was an American fabless semiconductor company based in Santa Clara, California. It developed low power x86 compatible microprocessors based on a VLIW core and a software layer called Code Morphing Software. Code Morphing ...

and other chip manufacturers also produced IA-32 compatible processors (e.g.

WinChip The WinChip series is a discontinued CPU electrical consumption, low-power Socket 7-based x86 central processing unit, processor that was designed by Centaur Technology and marketed by its parent company Integrated Device Technology, IDT. Overvie ...

). In the modern era, Intel still produced IA-32 processors under the Intel Quark

microcontroller A microcontroller (MC, uC, or μC) or microcontroller unit (MCU) is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Pro ...

platform until 2019; however, since the 2000s, the majority of manufacturers (Intel included) moved almost exclusively to implementing CPUs based on the 64-bit variant of x86,

x86-64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit extension of the x86 instruction set architecture, instruction set. It was announced in 1999 and first available in the AMD Opteron family in 2003. It introduces two new ope ...

. x86-64, by specification, offers legacy operating modes that operate on the IA-32 ISA for backwards compatibility. Even given the contemporary prevalence of x86-64, as of today, IA-32 protected mode versions of many modern operating systems are still maintained, e.g.

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

(until

Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. The successor to Windows 8.1, it was Software release cycle#Release to manufacturing (RTM), released to manufacturing on July 15, 2015, and later to retail on July 2 ...

Windows Server Windows Server (formerly Windows NT Server) is a brand name for Server (computing), server-oriented releases of the Windows NT operating system (OS) that have been developed by Microsoft since 1993. The first release under this brand name i ...

(until

Windows Server 2008 Windows Server 2008, codenamed "Longhorn Server" (alternatives: "Windows Vista Server" or "Windows Server Vista"), is the seventh major version of the Windows NT operating system produced by Microsoft to be released under the Windows Server b ...

) and the

Debian Debian () is a free and open-source software, free and open source Linux distribution, developed by the Debian Project, which was established by Ian Murdock in August 1993. Debian is one of the oldest operating systems based on the Linux kerne ...

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

distribution. In spite of IA-32's name (and causing some potential confusion), the 64-bit evolution of x86 that originated out of AMD would not be known as "IA-64", that name instead belonging to Intel's discontinued Itanium architecture.

Architectural features

The primary defining characteristic of IA-32 is the availability of 32-bit general-purpose

processor register A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-onl ...

s (for example, EAX and EBX), 32-bit

integer An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...

arithmetic and logical operations, 32-bit offsets within a segment in

protected mode In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as Memory_segmentation, segmentation, virtual mem ...

, and the translation of segmented addresses to 32-bit linear addresses. The designers took the opportunity to make other improvements as well. Some of the most significant changes (relative to the 16-bit 286 instruction set) are: ; 32-bit integer capability: All

general-purpose register A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-onl ...

s (GPRs) are expanded from 16

bit The bit is the most basic unit of information in computing and digital communication. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented as ...

s to 32 bits, and all arithmetic and logical operations, memory-to-register and register-to-memory operations, etc., can operate directly on 32-bit integers. Pushes and pops on the

stack Stack may refer to: Places * Stack Island, an island game reserve in Bass Strait, south-eastern Australia, in Tasmania’s Hunter Island Group * Blue Stack Mountains, in Co. Donegal, Ireland People * Stack (surname) (including a list of people ...

default to 4-byte strides, and non-segmented

pointers Pointer may refer to: People with the name * Pointer (surname), a surname (including a list of people with the name) * Pointer Williams (born 1974), American former basketball player Arts, entertainment, and media * ''Pointer'' (journal), the ...

are 4 bytes wide. ; More general addressing modes: Any GPR can be used as a base register, and any GPR other than ESP can be used as an index register, in a memory reference. The index register value can be multiplied by 1, 2, 4, or 8 before being added to the base register value and displacement. ; Additional segment registers: Two additional segment registers, FS and GS, are provided. ; Larger virtual address space: The IA-32 architecture defines a 48-bit segmented address format, with a 16-bit segment number and a 32-bit offset within the segment. Segmented addresses are mapped to 32-bit linear addresses. ; Demand paging: 32-bit linear addresses are virtual addresses rather than physical addresses; they are translated to physical addresses through a

page table A page table is a data structure used by a virtual memory system in a computer to store mappings between virtual addresses and physical addresses. Virtual addresses are used by the program executed by the accessing process, while physical addr ...

. In the 80386, 80486, and the original Pentium processors, the physical address was 32 bits; in the

Pentium Pro The Pentium Pro is a sixth-generation x86 microprocessor developed and manufactured by Intel and introduced on November 1, 1995. It implements the P6 (microarchitecture), P6 microarchitecture (sometimes termed i686), and was the first x86 Intel C ...

and later processors, the

Physical Address Extension In computing, Physical Address Extension (PAE), sometimes referred to as Page Address Extension, is a memory management feature for the x86 architecture. PAE was first introduced by Intel in the Pentium Pro, and later by AMD in the Athlon process ...

allowed 36-bit physical addresses, although the linear address size was still 32 bits.

Operating modes

References

{{Reflist, 30em, refs= {{cite web, title=Additional Predefined Macros, url=https://software.intel.com/content/www/us/en/develop/documentation/cpp-compiler-developer-guide-and-reference/top/compiler-reference/macros/additional-predefined-macros.html, work=software.intel.com, publisher=

, access-date=November 25, 2020, archive-date=February 15, 2021, archive-url=https://web.archive.org/web/20210215084323/https://software.intel.com/content/www/us/en/develop/documentation/cpp-compiler-developer-guide-and-reference/top/compiler-reference/macros/additional-predefined-macros.html, url-status=live {{cite web, title=ditto(1) Mac OS X Manual Page, url=https://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man1/ditto.1.html, work=BSD General Commands Manual, publisher=

Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

, access-date=August 3, 2013, date=December 19, 2008, quote=Thin Universal binaries to the specified architecture ..should be specified as "i386", "x86_64", etc., archive-date=June 2, 2012, archive-url=https://web.archive.org/web/20120602013413/https://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man1/ditto.1.html, url-status=dead {{cite web, last=Kemp, first=Steve, title=Running 32-bit Applications on 64-bit Debian GNU/Linux, url=http://www.debian-administration.org/articles/534, work=Debian Administration, access-date=August 31, 2013, archive-date=September 16, 2013, archive-url=https://web.archive.org/web/20130916160905/http://www.debian-administration.org/articles/534, url-status=dead {{cite web , first=Ronald W. , last=Green , title=What do IA-32, Intel 64 and IA-64 Architecture mean? , url=https://software.intel.com/en-us/articles/ia-32-intelr-64-ia-64-architecture-mean/ , website=software.intel.com , publisher=

, date=May 5, 2009 , access-date=December 19, 2014 , archive-date=December 19, 2014 , archive-url=https://web.archive.org/web/20141219144304/https://software.intel.com/en-us/articles/ia-32-intelr-64-ia-64-architecture-mean/ , url-status=live {{cite web, title=Supported Hardware, url=https://help.ubuntu.com/12.04/installation-guide/en.i386/ch02s01.html, archive-url=https://archive.today/20141219153039/https://help.ubuntu.com/12.04/installation-guide/en.i386/ch02s01.html, url-status=dead, archive-date=December 19, 2014, work=Ubuntu Help, publisher=

Canonical The adjective canonical is applied in many contexts to mean 'according to the canon' the standard, rule or primary source that is accepted as authoritative for the body of knowledge or literature in that context. In mathematics, ''canonical exampl ...

, access-date=August 31, 2013 Computer-related introductions in 1985 X86 architecture 32-bit computers

Architectural features

Operating modes

See also

References