Path: utzoo!utgpu!water!watmath!clyde!rutgers!rochester!PT.CS.CMU.EDU!andrew.cmu.edu!ws0n+ From: ws0n+@andrew.cmu.edu (Walter Ray Smith) Newsgroups: comp.sys.mac Subject: Re: Is Mac II flawed? Message-ID:Date: 11 Dec 87 01:04:58 GMT Organization: Carnegie Mellon University Lines: 18 In-Reply-To: <7630@eddie.MIT.EDU> > The SE compatibility mode consists of making each NuBus slot a 1MB > partition in a 16MB SE-like address space. ... > (Hey Apple, any good answers for this > seemingly backward-thinking design decision? It is certainly a backward-thinking design decision--thinking back to all the Mac software that assumes the top byte of an address is irrelevant. The "SE compatibility mode" (never thought of it that way...) is the hardware maintaining that illusion. Also, as far as I know, the current memory manager still uses the top bytes of its master pointers for flags, so the top byte of an address *must be* irrelevant under the Mac OS. A/UX is another story entirely... - Walt -- Walter Smith, CS graduate student, Carnegie-Mellon University uucp: ...!seismo!cmucspt!wrs (?) ARPA: Walter.Smith@andrew.cmu.edu usps: 5706 Darlington Rd.; Pittsburgh, PA 15217