64-bit Windows Part 5: A Summary Comparison of the Two Species of 64-bit Processors
So, we find that the Itanium processor and the x64 Opteron processor are very different. They both incorporate ingenious ideas for drastically increasing the performance of the processor that go far beyond just making them 64-bit capable. Compared purely as 64-bit processors, the Itanium’s massive floating point processing capability is impressive. But in implementing its Itanium innovations, Intel created a new instruction set, the EPIC instruction set, which is not backwardly compatible with the established x86 instruction set. To support x86 software, Intel had to build an x86 decoder into the Itanium processor. By contrast, AMD’s design of its Opteron x64 processor yielded a 64-bit processor that is fully backwardly-compatible with x86 software. Consequently, the x64 species of processor is not only compatible with x86 operating systems, but also does not compromise the performance of x86 applications.