IA32

IA-32, short for Intel Architecture 32-bit, is the 32-bit extension of the x86 instruction set architecture. Also referred to as x86-32, it was introduced by Intel with the 80386 processor in 1985 and became the dominant 32-bit platform for personal computers and servers for many years. IA-32 provides 32-bit general-purpose registers (EAX, EBX, ECX, EDX, ESI, EDI, EBP, ESP) and a 32-bit instruction pointer (EIP) and flags register (EFLAGS), along with a 32-bit addressing model.

In protected mode, IA-32 supports segmentation, paging, and virtual memory, while real mode and virtual-8086 mode preserve backward compatibility with older 16-bit software. The architecture uses segment selectors and the Global Descriptor Table (GDT) and Local Descriptor Tables (LDT), along with privilege levels (rings 0–3) for protection. It also supports advanced features such as the Task State Segment for task switching and sophisticated interrupt handling.

Over its lifetime IA-32 gained several extensions. Physical Address Extension (PAE) enables addressing beyond 4 gigabytes of RAM on 32-bit systems. SIMD instruction sets such as SSE and SSE2 were added in later generations to accelerate multimedia and scientific workloads. The design emphasizes compatibility with legacy software through real mode and virtual-8086 mode, while OS developers commonly used a flat 32-bit memory model in protected mode.

Legacy and successors: In the 2000s and 2010s, x86-64 (also called x64 or IA-32-64) extended IA-32 to 64-bit addressing, and Intel-64/AMD64 became the de facto standard for new hardware. IA-32 remains supported for compatibility on modern processors, but new software often targets the 64-bit architecture. IA-32 is distinct from IA-64 (Itanium).