Here’s an example for that: Apple needed to ship an x86_64 emulator for the transition, but that’s slow and thus make the new machines appear much slower than their older Intel-based ones. So, what they did was to come up with their own private instructions that an emulator needs to greatly speed up its task and added them to the chip. Now, most people don’t even know whether they run native or emulated programs, because the difference in performance is so minimal.