x64 architecture and instruction set
The original specification for a processor architecture extending the x86 processor and instruction set to 64 bits, named AMD64, was introduced by AMD in 2000. The first AMD64 processor, the Opteron, was released in 2003. Intel found itself following AMD’s lead and developed an AMD64-compatible architecture, eventually given the name Intel 64. The first Intel processor that implemented the 64-bit architecture was the Xeon, introduced in 2004. The name of the architecture shared by AMD and Intel came to be called x86-64, reflecting the evolution of x86 to 64 bits, and, in popular usage, this term has been shortened to x64.
The first Linux version supporting the x64 architecture was released in 2001, well before the first x64 processors were even available. Windows began supporting the x64 architecture in 2005.
Processors implementing the AMD64 and Intel 64 architectures are largely compatible at the instruction set level of user-mode...