M1 Chip

ARM chips aren't designed like typical x86 chips are, in the sense of everything but the kitchen sink. 

ARM chips, are RISC chips, that have limited instructions, and only run a small set of them, for whatever they're designed to run. By default, they're also designed within an entire board design, meaning they're not plug and play. You can't drop a new chip/different chip into ARM boards, typically. They know what resources they have, and where those are, on the board(Think mem allocations). 

So they design them, in such a way that allows the GPU to shut down and run CPU only, or turn off a section of memory if needed.etc