Yeah, except the CPUs are complex, you might not understand ALL the details of a working program (like randomising memory layout).
Plus not all speed-ups are made equal. Some speedups of a part of program can have no or even negative impact (as in making part of program faster slows down overall program execution).
Plus not all speed-ups are made equal. Some speedups of a part of program can have no or even negative impact (as in making part of program faster slows down overall program execution).