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From: ralphw@ius3.ius.cs.cmu.edu (Ralph Hyre)
Newsgroups: comp.sys.mac
Subject: Re: When will MacOS get virtual memory?
Keywords: multitasking protection multiuser mmu
Message-ID: <3375@pt.cs.cmu.edu>
Date: 22 Oct 88 13:37:56 GMT
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Interesting that timesharing and virtual memory are becoming popular
again.  Even though there are time proven techniques for managing scarce
resources, resources shouldn't be that scarce anymore.

Anyway, any plain vanilla 68000 can do multiuser & multitasking stuff.
AmigaDOS, Microware systems OS-9, and many early Unix vendors have
pretty effectively shown that.

What you want on a machine like a Mac where most of the applications 
are programmed in 'unsafe' implementations of languages, and compilers
generate code which can trash anything is memory PROTECTION.  This strongly
encourages the use of an MMU.

And once you have a MMU, you can easily do Virtual memory (which I consider 
sort of a last resort, for those who want a certain set of applications, but
don't have enough memory for them, is an MMU.  The Mac memory management system
is nifty enough that I suspect even multifinder could be patched up to provide
for a swapping MacOS, where whole application code resources (and maybe even 
their data spaces) can be put on a disk when they aren't in the foreground.
-- 
					- Ralph W. Hyre, Jr.
Internet: ralphw@ius3.cs.cmu.edu    Phone:(412) CMU-BUGS
Amateur Packet Radio: N3FGW@W2XO, or c/o W3VC, CMU Radio Club, Pittsburgh, PA
"You can do what you want with my computer, but leave me alone!8-)"