Today a friend asked why the software version will be marked for amd64 version, not intel64 it?
X86
X86 architecture (The X86 architecture) is a computer language instruction set executed by the microprocessor, it means a standard code abbreviation intel series general purpose computer, a general-purpose computer also identifies a set of instructions.
June 8, 1978, Intel released a new 16-bit microprocessor "8086", also ushered in a new era: x86 architecture was born.
In the history of 40 years in, x86 family has grown, he moved notebooks, servers, supercomputers from the desktop, but also a lot of frustration or restrict the development of competitors' writing device, during which so many processor architectures technology vendors and their history name, even though some are also closed unsustainable development, such as Apple has abandoned the PowerPC.
AMD64/x86-64
x86-64 sometimes simply referred to as "x64", and is a 64-bit microprocessor architecture to a corresponding instruction set, is the Intel x86 architecture extension products. "X86-64" 1999 by the AMD design, AMD first public 64 set to expand to IA-32, called x86-64 (later renamed AMD64). AMD64 on IA-32 architecture in a new 64-bit register, and is compatible with the earlier 16-bit and 32-bit software, allows the object existing x86-compiler AMD64 readily converted version.
Because AMD64 and Intel64 basically the same, a lot of software and hardware products are not inclined to any use of a vocabulary party to show that they are compatible for both architectures simultaneously. For this purpose, AMD original call this CPU architecture - "x86-64" is often used, as well as variants "x86_64". Other companies such as Microsoft and Sun use "x64" in marketing materials as an abbreviation for "x86-64" of.
On the introduction of "x86-64" supported the use of "AMD64" or "amd64" to refer to both AMD64 and Intel64 before many operating systems and products, especially those in the Intel entering this market.
EM64T
Intel的EM64T技术，EM64T技术官方全名是Extended Memory 64 Technology，中文解释就是扩展64bit内存技术。
EM64T本质上和AMD64一样都是IA-32的增强版本，Xeon借助于EM64T可实现高达1TB（40bit）的物理内存寻址和256TB（48bit）的虚拟内存寻址，并且良好地支持现有32位x86代码的执行，这一点跟AMD64无异，同时也是Intel开发EM64T的出发点—让现有的x86指令集能够执行64位代码，而继续保持对32位代码的良好兼容。
IA-64
Intel在之前已在Itanium处理器上使用了自家的64位IA-64技术，虽然说Intel 64也是64位，但两者并不兼容，即IA-64的软件不能直接在Intel 64上运行。Intel 64所用的x86-64是IA-32指令集的延伸，而IA-64则是另一款独立的架构，没有任何IA-32的影子。虽然IA-64可通过模拟来运行IA-32的指令，但指令在运行前需经转换，才能在IA-64上运行，导致其速度变慢。由于x86-64是从IA-32派生而来，因此运行IA-32与64位程序的表现也显得绰绰有余。
目前市场上Intel兼容处理器可以实现64位计算的主要有3种：
1) Intel IA64，基于安腾2处理器，不兼容32位应用，软件相对本模式的版本叫 xxx for Itanium 。
2) Intel EM64T，基于Xeon DP “Nocona”和MP处理器，兼容32位应用，软件相对本模式的版本叫 xxx for x86-64或者amd64。
3) AMD AMD64，基于Opteron处理器，兼容32位应用，软件相对本模式的版本叫 xxx for x86-64或者amd64。