Before they decided on PowerPC, they had a failed attempt at building their own RISC CPU:

https://thechipletter.substack.com/p/the-first-apple-silicon...

https://archive.org/details/scorpius_architecture

Apple definitely dabbled in silicon around that time, the headliner was the Aquarius RISC CPU project. They famously bought a Cray for it.

not "silicone" that's something else.

They were rolling their own north-bridge-ish chips at the same time for 2FX and later machines (all pre the power PC switch)

The first true ARM MMU design was Bob Welland's, who had joined Apple after his stint at Commodore (C900, Amiga 500). It doesn't look like traditional MMUs, because it needed to support the Newton OS and shared address spaces.

I stand corrected :)