This is exactly it. Also the reason why IA64 failed, and we're using amd's x86-64 instead. In more recent times, the argument is less relevant because the comp

This is exactly it. Also the reason why IA64 failed, and we're using amd's x86-64 instead. In more recent times, the argument is less relevant because the compatibility layer is software-side, see the mostly painless x86 -> ARM transition by Apple.