IA-32 (short for "Intel Architecture, 32-bit", sometimes also called i386) is the 32-bit version of the x86 instruction set architecture, first implemented in the Intel 80386 microprocessors 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 to refer to all x86 versions that support 32-bit computing.
The IA-32 instruction set was introduced in the Intel 80386 microprocessor in 1985 and, as of 2017 , remains supported by contemporary PC microprocessors. Even though the instruction set has remained intact, the successive generations of microprocessors that run it have become much faster. Within various programming language directives, IA-32 is still sometimes referred to as the "i386" architecture.
Intel is the inventor and the biggest supplier of IA-32 processors, and the second biggest supplier is AMD. For a while, VIA, Transmeta and others also produced IA-32 processors, but since the 2000s all manufacturers moved to the 64-bit variant of x86, x86-64.
The primary defining characteristic of IA-32 is the availability of 32-bit general-purpose processor registers (for example, EAX and EBX), 32-bit integer arithmetic and logical operations, 32-bit offsets within a segment in protected mode, 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 are described below.
|Operating mode||Operating system required||Type of code being run||Default address size||Default operand size||Typical GPR width|
|Protected mode||32-bit operating system or boot loader||32-bit protected-mode code||32 bits||32 bits||32 bits|
|16-bit protected-mode operating system or boot loader, or 32-bit boot loader||16-bit protected-mode code||16 bits||16 bits||16 or 32 bits|
|Virtual 8086 mode||16- or 32-bit protected-mode operating system||16-bit real-mode code||16 bits||16 bits||16 or 32 bits|
|Real mode||16-bit real-mode operating system or boot loader, or 32-bit boot loader||16-bit real-mode code||16 bits||16 bits||16 or 32 bits|
Thin Universal binaries to the specified architecture [...] should be specified as "i386", "x86_64", etc.
The Intel386 processor was the first 32-bit processor in the IA-32 architecture family. It introduced 32-bit registers for use both to hold operands and for addressing.
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