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From: hansen@cs.uiowa.edu.UUCP
Newsgroups: comp.sys.apple
Subject: Re: Apple //e upgrade to //gs
Message-ID: <8702251007.aa07502@SPARK.BRL.ARPA>
Date: Wed, 25-Feb-87 09:16:59 EST
Article-I.D.: SPARK.8702251007.aa07502
Posted: Wed Feb 25 09:16:59 1987
Date-Received: Fri, 27-Feb-87 21:08:59 EST
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In regard to multitasking:

I have looked into the problem from the micro and mini computer side of things
and have come to the conclusion that for true multitasking you absolutely must
have hardware protection between processes.

If you don't have this, then a bug in your printer spooler crashes your editor,
your neat alarm clock, your operating system master program, etc.  No process
has any protection from any of the others.  The system is really too complex
already for reliability.  The attempt at running n processes at the same time
without hardware protection produces n! as many opportunities for interacting
bugs.  The end result is that you simply can't come up with a working machine,
or at least working software that is acceptable to the majority (I realize
that a subset of users will be happy with this shortcoming, but even this
group will become convinced the first time a bug in the computer they're down
loading from in the background destroys an hour's work in the editor they wer
e using in the foreground.)

Thus the reason current micros don't have true multitasking is that they don't
have hardware process protection.  The 68000 doesn't have it, although the 
68010 and 68020 do.  The 6502 certainly doesn't, and thus the //gs in order
to be at least reasonably compatible, doesn't either.

Kurt