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Path: utzoo!watmath!clyde!rutgers!cbmvax!daveh
From: daveh@cbmvax.UUCP
Newsgroups: comp.sys.amiga,comp.sys.mac,comp.sys.atari.st
Subject: Re: Re: Mac vs. Amiga (vs. ST)
Message-ID: <1314@cbmvax.cbmvax.cbm.UUCP>
Date: Thu, 29-Jan-87 15:58:31 EST
Article-I.D.: cbmvax.1314
Posted: Thu Jan 29 15:58:31 1987
Date-Received: Fri, 30-Jan-87 06:23:49 EST
References: <8392@watrose.UUCP>
Organization: Commodore Technology, West Chester, PA
Lines: 87
Xref: watmath comp.sys.amiga:1769 comp.sys.mac:1017 comp.sys.atari.st:1152

> Keywords: Mac, Amiga, ST
> Xref: cbmvax comp.sys.amiga:1618 comp.sys.mac:937 comp.sys.atari.st:1063
> 
> 
> In article <636@mit-amt.MEDIA.MIT.EDU> ralph@ATRP.MEDIA.MIT.EDU (Amiga-Man) writes:
>> ...  [talks about advantages of Amiga]
>>- A true multitasking OS. I find this feature very important.
> 
> 	I'm really curious: just how great is multitasking?  I.e., how much do
> you, the typical Amiga owners, use this feature?  Even on Unix I find that the
> only thing I consistently use '&' for is printing, and on my ST I have a wide
> range of print spoolers to choose from.  ...
>
> I _DO_ envy your multitasking!  I'm just curious how useful it
> actually is.  I.e., is it that necessary in a personal computer,
> and is it worth the slow-down in execution?  Even though I would really _like_
> it, would I really use it that much?
> 
> 				- Jonathan Fischer

Well, first of all, even if you never experience a need for multitasking,
you get two things from it.  First of all, the Operating System uses it.
System devices, like disk driver, have a server task that operates them.
The DOS will generally send messages to these tasks, which then "take it
from there", often asynchronously.  The nice thing about this is that a
calling program isn't required to wait for the disk operation to finish
before going on.  Disk I/O is mostly waiting for the heads to move, so
as a background task you use very little CPU time on disk access (on the
Amiga, the floppy reads and writes are done by a custom chip during an
interlaced DMA slot, so you have even more CPU time available.  But on
any machine this can be a big win).  The multitasking system lets you very 
easily take advantage of CPU time that would otherwise be wasted in some 
kind of a wait loop.  Another example of system multitasking is Intuition, 
the graphic interface manager on the Amiga.  Intuition exists as a high
priority background task.  It monitors input events, like keyboard or
mouse actions.  Programs send messages to Intuition, asking for any
events Intuition has noticed; Intuition tells each program about only
those events its specifically concerned about.  As a separate task, 
Intuition will never miss mouse movements or key strokes, while in a single
tasking system you can very easily miss such things, or slow your 
program down trying not to miss any.  Also, the Intuition process as a
high level I/O server makes alot of sense when you consider that several
different tasks may all be asking about these events.  Since Intuition
is there, no task need know about any other running with it.

Now there's the multitasking I use myself, out of choice versus system
design.  Truthfully, I use multitasking on the Amiga much more than on
UNIX, mainly because the windowing/screening capabilities of the Amiga
let me run simultaneous interactive things much better than I can on
normal UNIX (may X-Windows on a UNIX system will change this).  I do the
same amount of multitasking on the Apollo workstations I use here, for 
basically the same reasons; the windowing.  To start off, I usually run 
a few background tasks, the print server, PopCLI (a new CLI window at the
touch of a key, just like on the Apollo), and Emacs if I'm on a machine
with enough memory.  I can start up Kermit and download from our VAX,
click that screen to the back (it keeps running, of course), and edit
or compile something while the download is taking place.  The ability
to multitask also completely eliminates the need for specially written
"desk accessory" or "RAM resident" programs, since any number of
programs can run together or stick around in memory; none of them have
to obey any special constraints.  And the result is much greater
efficiency; instead of my application program having to poll the system
whenever possible to find any request for a desk accessory, my program
just does what I intend to do with it.  And other tasks like WorkBench
or CLI can load an accessory program if I like.  

And finally, individual programs can benefit from multitasking.  First of
all, there's never any reason to kludge "DOS" type commands into a 
program, since you can always fire up a CLI window to do the job the
right way.  A program can implement things with tasks much more
efficiently and effectively than with standard polling methods.  One
controlling task can operate with an arbitrary number of servent tasks
using "software buss" messing protocols.  I think most folks feel
satisfied with single tasking because they've always done things that
way.  The more you use a system that multitasks well, like the Amiga
(or an Apollo or Sun), the more you feel frustrated with the old
single tasking systems.  At least, that's been my experience.


-- 
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Dave Haynie	{caip,ihnp4,allegra,seismo}!cbmvax!daveh

     "You can keep my things, they've come to take me home"
						-Peter Gabriel

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