Intel ARCHITECTURE IA-32 User Manual

IA-32 Intel® Architecture Processor Family Overview
1-7
Intel
®
Extended Memory 64 Technology
(Intel
®
EM64T)
Intel EM64T is an extension of the IA-32 Intel architecture. Intel
EM64T increases the linear address space for software to 64 bits and
supports physical address space up to 40 bits. The technology also
introduces a new operating mode referred to as IA-32e mode.
IA-32e mode consists of two sub-modes: (1) compatibility mode
enables a 64-bit operating system to run most legacy 32-bit software
unmodified, (2) 64-bit mode enables a 64-bit operating system to run
applications written to access 64-bit linear address space.
In the 64-bit mode of Intel EM64T, software may access:
• 64-bit flat linear addressing
• 8 additional general-purpose registers (GPRs)
• 8 additional registers for streaming SIMD extensions (SSE, SSE2
and SSE3)
• 64-bit-wide GPRs and instruction pointers
• uniform byte-register addressing
• fast interrupt-prioritization mechanism
• a new instruction-pointer relative-addressing mode
For optimizing 64-bit applications, the features that impact software
optimizations include:
• using a set of prefixes to access new registers or 64-bit register
operand
• pointer size increases from 32 bits to 64 bits
• instruction-specific usages

Intel ARCHITECTURE IA-32 Specifications

General

Instruction Set	x86
Instruction Set Type	CISC
Memory Segmentation	Supported
Operating Modes	Real mode, Protected mode, Virtual 8086 mode
Max Physical Address Size	36 bits (with PAE)
Max Virtual Address Size	32 bits
Architecture	IA-32 (Intel Architecture 32-bit)
Addressable Memory	4 GB (with Physical Address Extension up to 64 GB)
Floating Point Registers	8 x 80-bit
MMX Registers	8 x 64-bit
SSE Registers	8 x 128-bit
Registers	General-purpose registers (EAX, EBX, ECX, EDX, ESI, EDI, ESP, EBP), Segment registers (CS, DS, SS, ES, FS, GS), Instruction pointer (EIP), Flags register (EFLAGS)
Floating Point Unit	Yes (x87)