Path: utzoo!attcan!utgpu!watmath!watdragon!dahlia!swklassen
From: swklassen@dahlia.waterloo.edu (Steven W. Klassen)
Newsgroups: comp.sys.atari.st
Subject: Re: Multitasking on the ST
Message-ID: <15877@watdragon.waterloo.edu>
Date: 12 Aug 89 15:55:23 GMT
References: <8908021826.AA05333@ucbvax.Berkeley.EDU> <62441@linus.UUCP> <4050@hall.cray.com> <62828@linus.UUCP>
Sender: daemon@watdragon.waterloo.edu
Reply-To: swklassen@dahlia.waterloo.edu (Steven W. Klassen)
Organization: U. of Waterloo, Ontario
Lines: 38

In article <62828@linus.UUCP> rachamp@mbunix (Champeaux) writes:
>
>Now there's a point to debate.  Do you really need memory protection on a
>single user multi-tasking computer.  On a multi-user computer, memory
>protection is a necessity, since if one user's program crashes, you don't
>want to bring down the 50 other users.  On a personal computer, where cost
>is an important factor, is it really necessary?  (kind of sounds like the
>question "Is multi-tasking really necessary?" doesn't it?)
>It would, however, be really nice.

Here is a key issue in the multitasking debate: cost vs. performance.
While it is true that you are never going to match the performance
of a system designed (with hardware) for multitasking only through
software, one can come up with some pretty good compromises.  Minix
is a good example of this, sure its not as secure as Unix but then
again, security isn't as much of an issue on a single-user system
as it is on a mult-user system.  It seems reasonable to sacrifice
some security in order to keep cost down and performance up.  (Still
it would be nice if we had the hardware to make it efficient, but
since we don't we must do the best that we can with what we have.)

As for the usefulness of multitasking, it extends not just to the
end user (running lots of programs), but also to the programmer.
Quite often in large applications it is useful to have portions of
the system running in the background. 
Clearly it is more efficient and more secure to have this supported
by the OS rather than requiring the program itself to include all
the scheduling and security stuff.
ie. I would benefit (as a programmer) greatly even if only a limited
multitasking were allowed (system calls to provide low priority
background processes).  Users would benefit from faster running
programs since the cpu would not have to be left sitting idle most
of the time.


Steven W. Klassen
Computer Science Major
University of Waterloo