When implementing an OS avoiding Assembly is impossible. Even if intrisics are used instead, they are just another way of using Assembly like instructions.
There are lots of informations in this book, "Revolution in The Valley: The Insanely Great Story of How the Mac Was Made".
They used more than some assembly. Andy Hertzfeld:
"But most of the Lisa code was written in the Pascal programming language. Since the Macintosh had much tighter memory constraints, we needed to write most of our system-oriented code in the most efficient way possible, using the native language of the processor, 68000 assembly language. Even so, we could still use Lisa code by hand translating the Pascal into assembly language.
"We directly incorporated Quickdraw, Bill Atkinson's amazing bit-mapped graphics package, since it was already written mostly in assembly language. We also used the Lisa window and menu managers, which we recoded in assembly language from Bill's original Pascal, reducing the code size by a factor of two or so. Bill's lovely Pascal code was a model of clarity, so that was relatively easy to accomplish."
Also, about half the LOC in MacPaint were assembly.
When implementing an OS avoiding Assembly is impossible. Even if intrisics are used instead, they are just another way of using Assembly like instructions.
There are lots of informations in this book, "Revolution in The Valley: The Insanely Great Story of How the Mac Was Made".