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From: rachamp@mbunix.mitre.org (Richard A. Champeaux)
Newsgroups: comp.sys.atari.st
Subject: Re: Multitasking on the ST
Message-ID: <62828@linus.UUCP>
Date: 7 Aug 89 15:00:59 GMT
References: <8908021826.AA05333@ucbvax.Berkeley.EDU> <62441@linus.UUCP> <4050@hall.cray.com>
Sender: news@linus.UUCP
Reply-To: rachamp@mbunix (Champeaux)
Organization: The MITRE Corporation, Bedford, Mass.
Lines: 55

In article <4050@hall.cray.com> rosenkra@hall.UUCP (Bill Rosenkranz) writes:
>In article <62441@linus.UUCP> rachamp@mbunix (Champeaux) writes:
>
>=You asked for simple common uses for multi-tasking on the Amiga.  Here are
>=two of the more common, less demanding uses of multi-tasking that I do on my
>=Amiga 2000:
>=
>[describes a user-initiated edit/cli switch]
>
>this is not a good example. you are simply task switching, something that
>programs like revolver can do.
>
>[describes another user-initiated switch, disk full/cli delete scenario]
>
>this, again is a simple switch of which program is executing. i think the
>general topic concerns doing several tasks simultaneously (i.e. let the os
>kernel do the context switch based on some scheduling mechanism). this way
>you can be compiling something (or doing some database, raytrace, etc op)
>while you read mail, play a game, or compile another program.
>
>=Rich Champeaux  (rachamp@mbunix.mitre.org)
>

Agreed.  The two things I mentioned are not very demanding of a multi-tasking
OS, and could be performed by something like REVOLVER.  The original author
said he didn't want "look at me" examples, he wanted examples of things that
everyone might use.  To truely make use of running programs simultaneanously,
you need a program that requires no user input and will run for a long time.
Compiling programs doesn't quite fit the bill.  When I'm compiling programs,
rarely do I say, "Gee, I have 30 seconds while the compiler is running, lets
load up a game."  I have raytraced animations in the background while I'm 
writting programs, or I'm calling a BBS.  If the raytracer is put at a lower
priority than what I'm currently running, you almost can't tell it's there.
Best of all, you don't have to give up your computer for several days.

Ahh, the hell with it.  It's not worth arguing about.  You can lead a horse
to water, but you can't make him drink.  Let him die of thirst, if that's 
what he wants.

>
>without an mmu to police memory, the os has to do it. this is terribly
>slow, IMHO. you just don't want one task stepping on another.
>
>-bill
>rosenkra@boston.cray.com

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.

Rich Champeaux  (rachamp@mbunix.mitre.org)