Zitat:
x86-64 (also known as x64, x86_64 and AMD64) is the 64-bit version of the x86 instruction set. [...] The original specification was created by AMD, and has been implemented by AMD, Intel, VIA, and others. [...] 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. [...]
http://en.wikipedia.org/wiki/X86-64