IA-32

greek_zjb

IA-32 (Intel Architecture, 32-bit),
sometimes generically called x86-32, is the
instruction set architecture
of
Intel
's most
commercially successful
microprocessors
. This is a
32-bit
extension of
the original Intel
x86
processor architecture. This architecture defines the instruction
set for the family of microprocessors installed in the vast majority of personal
computers in the world.
IA-32 is Intel's 32-bit implementation of the x86
architecture, distinguished from the preceding
16-bit
x86
processors, and the later
64-bit
architecture
IA-64
implemented in
the
Itanium
microprocessors. IA-32 has had such longevity partially because of full
backwards compatibility.
The IA-32 instruction set is usually described as a CISC (
Complex Instruction Set Computer
)
architecture, though such classifications have become less meaningful with
advances in microprocessor design. Most modern x86 architectures (
K7
,
NetBurst
and
newer) are often referred to as post-RISC processors.

  
  Contents
  [
hide
]
  
1 History
2 Succeeding
       architectures
2.1 IA-64
2.2 AMD64
2.3 Intel 64

3 See also
4 External
       links
  

[
edit
] History
The IA-32 instruction set was introduced in the
Intel 80386
microprocessor in
1985
and remains the basis of most PC microprocessors over twenty years later. 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 was the inventor and is the biggest supplier of IA-32 processors,
but it is not the only supplier. The second biggest supplier is AMD. There are
other suppliers, but their volumes are small. As of 2007, Intel is moving to
x86-64, but still produces IA-32 processors such as
Celeron M
for laptops.
VIA Technologies
continues to produce the
VIA C3
/C7 family
of "pure" IA-32 devices, and AMD still produces the
Geode
line and mobile IA-32 processors. For a
time
Transmeta
produced IA-32 processors.
The IA-32 architecture was expanded by
AMD
in 2003 to natively support 64 bits,
creating a new derivative
x86-64
architecture. The first family of processors to support
this architecture, which AMD calls AMD64, was the
AMD K8
family of
processors. This was the first time any company other than Intel made
significant additions to the IA-32 architecture. Intel was forced to follow
suit, introducing modified
NetBurst
family processors, initially referred to as
"IA-32e" or "EM64T" and now called Intel 64 and almost
identical to AMD64. x86-64 is backwards compatible with 32-bit code without any
performance loss. For example, The Developers Manuals available from Intel on
the IA-32 architecture refer to IA-32 and IA-32e in tandem.
[
edit
] Succeeding
architectures
The original IA-32 instruction set has been evolved over time with the
addition of the multimedia instruction updates. Many new architectures,
including 64-bit ones, have since succeeded IA-32. However, the ultimate
evolution of IA-32 was when it was extended again to 64-bits, but of course at
that point it cannot be called IA-32 anymore; the 64-bit extension is called
x86-64
. It could
not be called
IA-64
as Intel had already used this label for the
Itanium
design (a
design which is not really an evolution of the IA-32 architecture). AMD's
AMD64
was the first
x86-64 instruction set designed. Later, Intel followed by imitating AMD's
design with what they call
Intel 64
(formerly IA-32e and EM64T).
[
edit
] IA-64
Main article:
IA64

Intel's IA-64 architecture is not directly compatible with the IA-32
instruction set, despite having a similar name. It completely discards all
IA-32 instructions, and starts from scratch with a completely different
instruction set as well as using a
VLIW
design instead of
out-of-order execution
. IA-64 is the
architecture used by the
Itanium
line of processors. Itanium initially had
hardware-support for IA-32, but it was very slow. Intel shifted to the use of a
software
emulator
instead. The nomenclature "IA-64" means "Intel Architecture,
64-bit", but the connection with IA-32 is only in the name.
Further improvements are:
Sixteen times
     the number of general purpose registers (now 128)Sixteen times
     the number of floating point registers (now 128)Register
     rotation mechanism to keep values in registers over function calls
[
edit
] AMD64
Main article:
x86-64

AMD
's AMD64
instruction set, initially called x86-64, is largely built on top of IA-32, and
thus maintains the
x86
family heritage, despite having a different name. While extending the
instruction set, AMD took the opportunity to clean up some of the odd behavior
of this instruction set that has existed since its earliest 16-bit days, while
the processor is operating in 64-bit mode.
Further improvements are:
Two times the
     number of general purpose registers (now 16)Two times the
     number of SSE registers (now 16)The general
     purpose registers are now truly general-purpose registers and are no
     longer restricted.Most of the
     functionality of the segment registers has been deprecated, since their
     usage has steadily declined even during the IA-32 days.
[
edit
] Intel 64
Main article:
x86-64#Intel_64

By February 2004, Intel announced the
Intel 64
instruction set, formerly known as
Yamhill
. It was
derived from AMD's
AMD64
.
Intel 64 is generally compatible with code written for the AMD64, though it
lacks some AMD64 features. Intel started using the set starting with the
Xeon
Nocona core in
late 2004, introducing it to the desktop market with the
Pentium 4
E0 revision in early 2005.
[
edit
] See also
x86
Wintel
IA-64
x86-64
(AMD's
     "AMD64" and Intel's "Intel64")
List of AMD microprocessors
List of Intel microprocessors
IA-4
IA-8
IA-16
Intel P6
NetBurst
Intel Core microarchitecture
Microarchitecture

[
edit
] External links
Free
     IA-32 documentation, provided by Intel
Retrieved from "
http://en.wikipedia.org/wiki/IA-32
"
Categories
:
X86 architecture



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