The Secret Apple M1 Coprocessor
I recall a relevant piece of history where the Intel 286 didn't have the ability to drop from the new protected mode back to real mode without a full system reset. A team at IBM eventually figured out that with a well crafted dance of instructions this could be achieved by taking advantage of specific quirks within the chip.By the time the 386 was released, this method was so common that Intel had to preserve these quirks to maintain compatibility with existing software. Apple may find themselves in a similar situation if they're not careful.