From: thompson@kuhub.cc.ukans.edu
Newsgroups: comp.sys.amiga.advocacy
Subject: OS/2 vs. AmigaOS (was Re: Amiga 4000/Atari Falcon)
Date: 28 Aug 92 17:57:48 CDT
Organization: University of Kansas Academic Computing Services

In article <1992Aug28.203809.12523@endicor.com>, tsarna@endicor.com (Ty Sarna) writes:
> 
> Huh? What on earth are you talking about. Go look up "real-time
> operating system" and find out what it means. As I said, something
> either is or isn't realtime, there is no inbetween.
> 
> I never said anything about "unfathomable somethings" that made AmigaOS
> special.  There are plenty of realtime OSes around.  QNX, VMS, even SVR4
> (though that's a bit wierd).  There are also plenty that aren't, such as
> Unix and OS/2.  Realtime has well-defined uses, such as control of
> physical processes.  Multimedia is another example.  It's much easier to
> keep video and audio in sync on a realtime system, since it makes
> performance guaruntees that can be depended on.  It's not impossible
> on non-realtime platforms, but it requires a little more work.

OS/2's Multimedia extensions probably qualify it as a real time
system.

> 
> I don't think you have any clue what I was talking about.  Where on
> earth did you get the impression that I said the Amiga was somehow
> magicly better and unique? Realtime is nothing special, it's just an OS
> feature, like VM.  Some have it, some do not.  OS/2 has VM, the Amiga
> does not.  AmigaOS is a realtime OS, OS/2 is not.  It's a design
> choice, and it means that each OS is better suited to some applications

I don't think IBM sat down at the table one day and said, "Let's not
make OS/2 a realtime os."  Having VM does not mean you can't have
a realtime os.  VM can be turned off.  You can lock an application
in memory.  Etc...

> that the other OS is.  So what's new? OS design has always been a matter
> of tradeoffs.  Heck, name ANYTHING about computers that isn't a matter
> of tradeoffs.  There's nothing magical about that. 
> 
> It means the OS makes performance guaruntees and is guarunteed to behave
> the same under the same conditions for certain types of things. For
> example, on the Amiga the highest priority task(s) that are ready to run are
> always guarunteed to be run. A lower priority task will never run when a
> higher priority task is runnable. Other OSes handle this differently, to
> guaruntee that a runnable task always runs at least once in a while.
> That's not good or bad. That's a design tradeoff.

Well, you just turn off background execution in OS/2, and then the
task doesn't run "at least once in a while."  There is no tradeoff.
> 
> Realtime also means determinism. For example, there are very few VM
> systems that are realtime (there are a few, but they are relatively rare
> and OS/2 is not one of them). The reason for this is that a section of

VMS uses virtual memory.  You said it was realtime.  It is a pretty
run of the mill os.

> code can't be guarunteed to always take the same number of cycles to
> run under the same circumstance when the data or code memory that has to
> be accessed might have to be swapped in. The same code might take vastly
> different amounts of time to run depending on VM.
> 

What can be guaranteed in a multitasking system?  Even with no VM,
task A can be done in by task B, unless task be is suspended.

> It also usually implies that the OS is relatively low-overhead, and the
> task switch time is minimized (at the cost of some features)
> 

As said earlier, realive to what?  

> Really, if you're going to insinuate that one OS doesn't have feature X
> and demand someone prove that another doesn't have it, don't you really
> thing you should understand, at least in basic terms, what X *is* first,
> before you go off flaming people? I entered this conversation in a

I think we all can agree on what real time is.  The question before us
is why you think AmigaOS is real time and OS/2 is not.  I don't agree.
I would invite civilized debate on the subject.

> civilized manner, trying to correct an error and perhaps eduacate a bit
> without taking sides, and you jump right in and start flaming. 
> 
> I merely pointed out a feature that the one OS has that yours lacks, and
> you attack me for that. Do you know which system I use and/or prefer?

What difference does that make?  You could prefer an Osbourne computer,
but that doesn't change the central question.

> Did you even bother to find out? No. Because I pointer out a difference,
> not even a better/worse difference mind you, but a simple difference in
> philosophy, I'm automaticly the enemy. Sheesh. And you called someone
> else paranoid? What does this say about you?
> 
> 
> -- Ty, who for the record is at this very second working on two systems,
> one of which is realtime and one of which has VM, and likes them equally.
> 
> --
> Ty Sarna				           tsarna@endicor.com

-- 
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|  University of Kansas              |  thompson@ukanvax.cc.ukans.edu        |
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