Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: Multitasking at home is great!! (Was Reality check: ....)
Message-ID: <17289@cbmvax.commodore.com>
Date: 9 Jan 91 18:45:44 GMT
References: <1990Dec13.155848.8152@maytag.waterloo.edu> <1990Dec22.082240.2443@news.iastate.edu> <26060@uflorida.cis.ufl.EDU> <MWM.91Jan5225918@fenris.relay.pa.dec.com> <17193@cbmvax.commodore.com> <MWM.91Jan7154817@raven.relay.pa.dec.com> <17210@cbmvax.commodore. <M
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 42

In article <MWM.91Jan8110848@raven.relay.pa.dec.com> mwm@raven.relay.pa.dec.com (Mike (My Watch Has Windows) Meyer) writes:

>Then again, I'll could decide that "true" multitasking means "no task
>can ever be completely blocked out, unless the user specifically
>allows it to happen by tagging the blocked task". That makes a lot
>more sense to me than just not allowing low priority tasks to starve
>higher priority ones. But then the Amiga doesn't have "true"
>multitasking.

Except, of course, your definition won't permit an operating system to be 
support both "true" multitasking and "realtime" response.  To be real time,
or even close to it, you need deterministic behavior.  On the Amiga, a task
can get very close to this by bumping its priority up, since it will be
wholly unaffected by all tasks at a lower priority.  Any system that gives
CPU time to lower priority tasks cannot easily guarantee that the higher
priority tasks get anything even close to realtime response.  

While not every multitasking OS tries to get close to realtime response, your
restriction is nothing you'd expect to find in the average multitasking system,
realtime or not.  Whereas most every general purpose multitasking operating
system would support my previous restriction.  And in general, most of these
make the fact they you are mulitasking hidden from the programmer.  That's
certainly not true with TSRs, which are a hack, or desk accessories, which
have to be specially written.  But under Multifinder, one of those cooperative
multitaskers, programs have to be specially written too in order to be
multitasked.  There are plenty of programs that can run for very long 
periods of time without naturally requiring a function call.  Basically, any 
program that's CPU intensive, rather than interactive.  My restriction is 
hardly an artificial restraint.  From what I've seen of them, AmigaOS, OS/2, 
UNIX, VAX/VMS, Aegis, TOPS-20, RSTS, OSK, and probably a few I've missed 
exhibit this expected behavior.  While what you consider to be multitasking 
depends on definition, a wacky restriction designed to exclude mainly the 
Amiga OS is silly, and you know it.

>	<mike


-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
	"Don't worry, 'bout a thing. 'Cause every little thing, 
	 gonna be alright"		-Bob Marley