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From: korn@eris.BERKELEY.EDU (Peter "Arrgh" Korn)
Newsgroups: comp.sys.mac
Subject: Re: multitasking on the Mac
Message-ID: <2328@jade.BERKELEY.EDU>
Date: Sat, 24-Jan-87 00:44:26 EST
Article-I.D.: jade.2328
Posted: Sat Jan 24 00:44:26 1987
Date-Received: Sat, 24-Jan-87 13:52:48 EST
References: <861@sdcc7.ucsd.EDU>
Sender: usenet@jade.BERKELEY.EDU
Reply-To: korn@eris.BERKELEY.EDU (Peter "Arrgh" Korn)
Organization: University of California, Berkeley
Lines: 28

In article <861@sdcc7.ucsd.EDU> ln63wzb@sdcc7.ucsd.EDU (Grobbins) writes:
>
>What difficulties, specifically, would hamper the implementation of
>a true multitasking operating system on the Mac?  I'm curious about
>the details, hardware and software.  What necessary hardware does
>the machine lack?  What about the existing software would cause
>dire headaches for the implementor of a multitasking operating 
>system on the Mac?

It's my understanding (from a quick chat with Andy Hertzfield at the
MacWorld Expo) that the mac stores too much information for each program
in low-memory globals for the mac to be able to do context switched
effeciently  (in other words, every time you switch tasks you would
have to move around too much information, thus making each task switch
too slow to make multi-tasking effecient enough to be usable).

Additionally, without hardware MMU doing the task switching, it's
possible for one program to crash the machine, including all the other
programs currently running.  This is one problem that the Amiga is
rather prone to.

Anyone with a better explanation?

Peter
-----						  
Peter "Arrgh" Korn		         Hacker?  Me?  A hacker?  No, actually
korn@ucbvax.Berkeley.EDU			 I'm a mac-er.  All's we do is
{decvax,dual,hplabs,sdcsvax,ulysses}!ucbvax!korn            make library calls.