Citation needed. Different from Anand's mentioning of "custom designed implementation of ARM ISA" on his webpage without any proof and further copied and taken to Wikipedia. One non-verified source cannot be trusted, sorry. Of course the chip is a custom design ( as it mentioned @ Wikipedia ), because ARM generally do not provide the peripherals and you can "bolt" whatever you like. Apple may be a big company, but they definitely lack the skill set to do such large chips themselves. The wild rumor goes to their attempt to ditch BRCM for wifi's chips for ages, something that would have happened if they had the resources to design something themselves. Not to mention the huge chunk of chip on the new macbook 12", rumored to be from the acquisition of Anobit, which if you have some knowledge of design is at least 4 generations behind. That of course is a speculation, much like Anand's quote of "custom ISA implementation" from A8 and onward, but at least the nm process can be seen to be quite old.