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 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...

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 Intel 8086 microprocessor and its 8088 variant. The 8086 was introd ...

instruction set architecture In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ' ...

, designed by

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...

and first implemented in the

80386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistors microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

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 closely associated with that thing or concept. Etymology The words ''metonymy'' and ''metonym'' come from grc, μετωνυμία, 'a change of name' ...

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. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

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, 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 of ...

s offered by the

80486 The Intel 486, officially named i486 and also known as 80486, is a microprocessor. It is a higher-performance follow-up to the Intel 386. The i486 was introduced in 1989. It represents the fourth generation of binary compatible CPUs following the ...

, 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 semiconductor company based in Santa Clara, California, that develops computer processors and related technologies for business and consumer markets. While it initially manufactur ...

. During the 1990s,

VIA Via or VIA may refer to the following: Science and technology * MOS Technology 6522, Versatile Interface Adapter * ''Via'' (moth), a genus of moths in the family Noctuidae * Via (electronics), a through-connection * VIA Technologies, a Taiwan ...

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 was a low-power Socket 7-based x86 processor designed by Centaur Technology and marketed by its parent company IDT. Overview Design The design of the WinChip was quite different from other processors of the time. Instead o ...

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

Intel Quark Intel Quark is a line of 32-bit x86 SoCs and microcontrollers by Intel, designed for small size and low power consumption, and targeted at new markets including wearable devices. The line was introduced at Intel Developer Forum in 2013, and d ...

microcontroller A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...

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 version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mod ...

. 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 2018, IA-32 protected mode versions of many modern operating systems are still maintained, e.g.

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 ...

(until

Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on J ...

;

Windows 11 Windows 11 is the latest major release of Microsoft's Windows NT operating system, released in October 2021. It is a free upgrade to its predecessor, Windows 10 (2015), and is available for any Windows 10 devices that meet the new Windows 11 ...

requires

-compatible processor for x86 versions) and the

Debian Debian (), also known as Debian GNU/Linux, is a Linux distribution composed of free and open-source software, developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993. The first version of D ...

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 ...

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 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-only. ...

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

integer An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign (−1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...

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 virtual memory, paging and safe multi-tasking d ...

, 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 described below. ; 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-only. ...

s (GPRs) are expanded from 16

bit The bit is the most basic unit of information in computing and digital communications. 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 represente ...

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: Places * Pointer, Kentucky * Pointers, New Jersey * Pointers Airport, Wasco County, Oregon, United States * The Pointers, a pair of rocks off Antarctica People with the name * Pointer (surname), a surname (including a l ...

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 the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are used by the program executed by the accessing process, ...

. In the 80386,

, 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 introduced the P6 microarchitecture (sometimes termed i686) and was originally intended to replace the original P ...

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, 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 an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...

, 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=live {{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 example ...

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

Architectural features

Operating modes

See also

References