From: tsarna@endicor.com (Ty Sarna)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Amiga 4000/Atari Falcon
Date: 28 Aug 92 20:38:09 GMT
Organization: Endicor Technologies, Inc., San Antonio, Texas

In article <1992Aug28.185823.26687@ctr.columbia.edu> jerry@connection.prospect.com (Jerry Shekhel) writes:
> tsarna@endicor.com (Ty Sarna) writes:
> >>
> >> AmigaOS is a real-time OS?  Since when?  What real-time features does it
> >> have that OS/2 does not?
> >
> >Since day 1.  "What real time features does it have" is a
> >semi-nonsequiter.  Something is either real-time or it isn't.
> 
> Oh, I see.  It's that special something -- something intangible and
> unfathomable to most human beings -- that makes the AmigaOS what it is.

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.

> This reminds me of the old Macintosh ads that used to say, "The Macintosh is
> not just another computer; it was designed from the chip up to be different
> from others and graphical in nature."  Yeah right.  Is that why I can run
> Mac software on an Atari ST, the ultimate in bare bones vanilla hardware?

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
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. 

> >Do you understand what makes a realtime OS
> >different? I'm not trying to be insulting, it's just that many people
> >don't understand what realtime means or why you'd want it.
> 
> OK, what *does* it mean?  And while you're at it, please list some reasons
> why OS/2 is less real-time than AmigaOS.

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.

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
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.

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

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
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?
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

	"Starring faces, set in celluloid,
		Welcome to the late show, starring null and void"