Executor used some fiendishly clever tricks to achieve performance on 1990s hardware at the expense of portability (e.g. the possibility of 64-bit support). Advanced Mac Substitute has different priorities and doesn't use any code from Executor.
However, ROMLib looks like a good source of unofficial system documentation, which I expect I'll be consulting in the future as I work on parts where Apple's docs become less detailed.
However, ROMLib looks like a good source of unofficial system documentation, which I expect I'll be consulting in the future as I work on parts where Apple's docs become less detailed.