Intel IA-32 - Manual (Page 49)

Vol. 3A 2-1
CHAPTER 2
SYSTEM ARCHITECTURE OVERVIEW
IA-32 architecture (beginning with the Intel386 processor family) provides extensive support
for operating-system and system-development software. This support offers multiple modes of
operation, which include:
•
Real mode, protected mode, virtual 8086 mode, and system management mode. These are
sometimes referred to as legacy modes.
•
IA-32e mode (added by Intel
®
Extended Memory 64 Technology). IA-32e mode operates
in one of two sub-modes: 64-bit mode or compatibility mode.
The IA-32 system-level architecture and includes features to assist in the following operations:
•
Memory management
•
Protection of software modules
•
Multitasking
•
Exception and interrupt handling
•
Multiprocessing
•
Cache management
•
Hardware resource and power management
•
Debugging and performance monitoring
This chapter provides a description of each part of this architecture. It also describes the system
registers that are used to set up and control the processor at the system level and gives a brief
overview of the processor’s system-level (operating system) instructions.
Many features of the IA-32 system-level architectural are used only by system programmers.
However, application programmers may need to read this chapter and the following chapters in
order to create a reliable and secure environment for application programs.
This overview and most subsequent chapters of this book focus on protected-mode operation of
the IA-32 architecture. IA-32e mode operation, as it differs from protected mode operation, is
also described.
All IA-32 processors enter real-address mode following a power-up or reset (see Chapter 9,
“Processor Management and Initialization”). Software then initiates the switch from real-
address mode to protected mode. If IA-32e mode operation is desired, software also initiates a
switch from protected mode to IA-32e mode.