Re: Is Mac II flawed?

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Article #22747

#22747

From: Walter Ray Smith
Date: Fri, 11 Dec 1987 01:04

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> 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

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Path: arc1-ca.pugleaf.net!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: <MVjoGuy00V4Dx0w1O0@andrew.cmu.edu>
Date: 11 Dec 87 01:04:58 GMT
Organization: Carnegie Mellon University
Lines: 18
In-Reply-To: <7630@eddie.MIT.EDU>