x86-64 is a 64-bit superset of the instruction set that makes up the x86 architecture.
The x86-64 instruction set was designed by AMD (called AMD64), and supported by Intel’s x86s (called Intel64, though originally called IA-32e and EM64T).
Therefore, x86-64 (or simply x64) refers to both AMD64 and Intel 64, which are two nearly identical implementations.
x86-64 is not the same as IA-64, as IA-64 is the underlying architecture for Intel’s Itanium line of processors.
History of x86-64 (AMD64 and Intel 64)
The AMD64 architecture is implemented by AMD’s Athlon 64, Athlon 64 FX, Athlon 64 X2, Turion 64, Turion 64 X2, Opteron, and Sempron processors. The first processor running on AMD64 was the Opteron, released in April 2003.
Meanwhile, Intel’s implementation of x86-64 (called Intel 64), is used in new versions of Pentium 4, Pentium D, Pentium Extreme Edition, Celeron D, Xeon, and Pentium Dual-Core processors, and in all Core 2 versions.
AMD created AMD64 as a completely different alternative to the IA-64 architecture from Intel and Hewlett-Packard. It was first announced by AMD as x86-64 in August 2000, as it would be an evolution to the existing dom architecture, and opposed to Intel’s idea of creating an entirely new 64-bit architecture (the IA-64).
Intel had to adapt to what AMD created (it had always been the other way around), creating an extension of its own line of x86 processors, giving rise to the Intel 64.
The name changed several times, at first it was referred to as IA-32e (for IA-32 extensions), then in March 2004 its official name was EM64T (Extended Memory 64 Technology). Finally into 2006, Intel started calling it the Intel 64, just like AMD does with the AMD64.
Differences between AMD64 and Intel 64
There are very small differences between the two sets of instructions. Compilers generally produce binaries that work on both AMD64 and Intel 64.
The small differences are only important to compiler developers and operating system developers.
Related:
IA-64.
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Alegsa.com.ar (2016). Definition of x86-64 – ALEGSA url: https:///Dec/x86-64.php
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