Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!spool2.mu.edu!uunet!cbmvax!cbmehq!cbmger!peterk
From: peterk@cbmger.UUCP (Peter Kittel GERMANY)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Help --> How to prevent the visit from the dreaded guru
Message-ID: <699@cbmger.UUCP>
Date: 8 Jan 91 08:44:17 GMT
References: <611@caslon.cs.arizona.edu> <1991Jan4.203339.8800@maytag.waterloo.edu> <1991Jan5.200226.19718@msuinfo.cl.msu.edu>
Reply-To: peterk@cbmger.UUCP (Peter Kittel GERMANY)
Organization: Commodore Bueromaschinen GmbH, West Germany
Lines: 30

In article <1991Jan5.200226.19718@msuinfo.cl.msu.edu> dailey@frith.uucp (Chris Dailey) writes:
>
>I don't care much about existing programs.

I hope you wear fireproof clothes. The Amiga is *not* a machine
for only exercising in programming, it is used in the real world
with existing programs. You actually can buy some!

>Even fake memory protection would due for many of us.  How about a
>command like "run such and such a program so it doesn't touch anything
>other than the OS".  It gets its own space, tucked away from the rest of
>the system?

I fear I can't explain this too well (perhaps someone other could
cut in): In AmigaOS (and in most other current OS's) you can't draw
a sharp line between program-owned and system-owned memory, because
of all that message passing to and fro. The Amiga implementation of
the message system is very fast, because it works with shared memory
so that the contents needs not to be copied. And these messages are
bidirectional, containing perhaps different data on reply. And all
this may happen asynchroneously. - In addition there are many data
structures that are created and owned by the system on demand of a
program, but this program also must be able to access these data.

You see, it's simply not possible to define the "own space" of a
normal Amiga program, so it also can't be easily protected by a MMU.

-- 
Best regards, Dr. Peter Kittel  // E-Mail to  \\  Only my personal opinions... 
Commodore Frankfurt, Germany  \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterk