I have a question. and i am probably confusing myself by thinking this.
the mac plus ROM is 128K correct?
Well i am looking at early mac schematics posted elseware, its only addressed up to A16 then skips to A20 so its in the 400000 address space.
Problem is, A16 can only address up to 64K. so how can you drop 128K roms in there without needing A17?
another point to ponder, if you dumped the 64K ROM out of a macintosh, how is it not 128kbytes?
because i noticed both ROMs are in parallel. only difference being, its each ROM serves 1 byte of a full word. so it would be 64K Words, and 128K bytes on an early 512k mac, right? or am i confusing myself here.
the mac plus ROM is 128K correct?
Well i am looking at early mac schematics posted elseware, its only addressed up to A16 then skips to A20 so its in the 400000 address space.
Problem is, A16 can only address up to 64K. so how can you drop 128K roms in there without needing A17?
another point to ponder, if you dumped the 64K ROM out of a macintosh, how is it not 128kbytes?
because i noticed both ROMs are in parallel. only difference being, its each ROM serves 1 byte of a full word. so it would be 64K Words, and 128K bytes on an early 512k mac, right? or am i confusing myself here.