x86-64 - WikipediaAMD Opteron, the first CPU to introduce the x86-64 extensions in April 2003 The five-volume set of the x86-64 Architecture Programmer's Manual, as published and distributed by AMD in 2002 x86-64 (also known as x64, x86_64, AMD64, and Intel 64)[note 1] is a 64-bit version of the x86 instruction set, first announced in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mod
