"Various names are used for the instruction set. Prior to the launch, x86-64 and x86_64 were used, while upon the release AMD named it AMD64. Intel initially us

"Various names are used for the instruction set. Prior to the launch, x86-64 and x86_64 were used, while upon the release AMD named it AMD64. Intel initially used the names IA-32e and EM64T before finally settling on 'Intel 64' for its implementation. Some in the industry, including Apple, use x86-64 and x86_64, while others, notably Sun Microsystems (now Oracle Corporation) and Microsoft, use x64. The BSD family of OSs and several Linux distributions use AMD64, as does Microsoft Windows internally." "The x86-64 architecture is distinct from the Intel Itanium architecture (formerly IA-64). The architectures are not compatible on the native instruction set level, and operating systems and applications compiled for one cannot be run on the other." https://en.wikipedia.org/wiki/X86-64#cite_note-11 https://en.wikipedia.org/wiki/X86-64#cite_note-11