Path: utzoo!attcan!uunet!munnari.oz.au!uhccux!ames!think!zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!apple!uokmax!d.cs.okstate.edu!minich
From: minich@d.cs.okstate.edu (Robert Minich)
Newsgroups: comp.sys.mac.misc
Subject: Re: New MS Windows (?)
Message-ID: <1990Jun1.163335.29479@d.cs.okstate.edu>
Date: 1 Jun 90 16:33:35 GMT
References: <15006@dime.cs.umass.edu>
Organization: Oklahoma State University
Lines: 22

|>By protection, I mean that if a program tries to address a chunk of memory 
|>it doesn't own, it traps and gets kicked out.  This seems to be a vital 
|>element to multitasking, since it protects applications from each others' 
|>bugs.  If System 6/7 do have this, is a PMMU needed?
 
|If I'm thinking of what you're thinking of...then no PMMU is needed.  But 
|I hardly qualify as a mac memory expert.

  Bzzzt - memory protection DOES require a PMMU (built in to the 68030) 
unless the system wanted to trap EVERY memory reference. That would be sort 
of like SoftPC, which is slow. :-) Sys 6 and 7 do/will not have memory
protection. (sigh) Apple has said that it will appear in a "future"
system (please, dear God, sys 8!!!)  as will preemptive multitasking.
Memory protection looks to be quite an undertaking if we don't want tons
of applications broken. Perhaps this will come with a complete rewrite
of the OS, using that 20/20 hindsight!

-- 
| _    /| | Robert Minich             |
| \'o.O'  | Oklahoma State University |  
| =(___)= | minich@a.cs.okstate.edu   | 
|    U    | - Bill sez "Ackphtth"     |