Actually, the stack pointer is taken from $00000000, and the starting address from $00000004...
By the way, the starting address for some (most?) Mac ROMs is of the form $40800000 -- that way is both compatible with 32-bit addressing, as expected upon reset ($40x00000 is the start of the several ROM images); and with 24-bit addressing, which maps the ROM to $800000.
BTW2... the SE and others (but not the SE/30) do not use any VIA bit for toggling the ROM overlay mode -- the first access to the ROM within its usual address range switches it!
By the way, the starting address for some (most?) Mac ROMs is of the form $40800000 -- that way is both compatible with 32-bit addressing, as expected upon reset ($40x00000 is the start of the several ROM images); and with 24-bit addressing, which maps the ROM to $800000.
BTW2... the SE and others (but not the SE/30) do not use any VIA bit for toggling the ROM overlay mode -- the first access to the ROM within its usual address range switches it!