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.<p>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.