x64 ~ A processor architecture based on the 32-bit IA-32 (x86) architecture with extensions for the execution of 64-bit software. AMD produced the first instances of x64- based processors the AMD64 processors-€”also referred to with the term- x86-64. x64-based (oth)~ Pertaining to the combination of a 64-bit Windows operating system and microprocessors that natively support the x86 for extended systems (x64) 64-bit instruction set. Examples include AMD Opteron and Intel Xeon with 64-bit extension technology processors.