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From: daveh@cbmvax.cbm.UUCP (Dave Haynie)
Newsgroups: net.micro.mac
Subject: Re: Re: Re: Multitasking Considered Useless?
Message-ID: <649@cbmvax.cbmvax.cbm.UUCP>
Date: Mon, 18-Aug-86 15:27:32 EDT
Article-I.D.: cbmvax.649
Posted: Mon Aug 18 15:27:32 1986
Date-Received: Wed, 20-Aug-86 05:46:45 EDT
References: <3218@ism780c.UUCP>
Organization: Commodore Technology, West Chester, PA
Lines: 78

>
> In article <617@cbmvax.cbmvax.cbm.UUCP> daveh@cbmvax.cbm.UUCP (Dave Haynie) writes:
>>>
>>>>No, the mac WASN'T designed for multi-tasking with stuff built into
>>>>the ROM for it like with the amiga, but the time for it is LONG overdue!
>>>>
>>> Oh come on!  The Mac has as much ROM support for multi-tasking
>>> as the Amiga :-)
>
> You seem to have missed my ":-)" symbol!  The Amiga stuff is in
> write-protected RAM.  Thus, the Mac has as much *ROM* support for
> multi-tasking, i.e., none.

OK, I'll give ya that one.  For the moment.

>>It would be better stated that without an MMU, sloppy programming in a
>>multitasking environment is dangerous.  With the MMU, if I allocate a 1K
>>chunk of memory and then write to it as a 2K chunk, the hardware protects
>>it from being clobbered, whereas without the MMU I could stomp on memory
>>being used by another process or task.  But its still my error that's
>>causing the problem.  In a properly written program, I won't have the
>>ability to clobber the memory of another task.
>
> But what about the person using commercial software?  There seem to be
> a hell of a lot of sloppy programmers out there!  I don't want to do
> any serious work under multi-tasking unless I know the program is safe
> or I have an mmu to protect me from other peoples mistakes.

That's certainly TRUE.  When you consider that many of the programmers out
there haven't written for anything other than an IBM PC, though, you can
understand this.  It took awhile for lots of good MAC applications to be
written, much of this was learning curve, since the MAC was a very new
kind of machine that could do alot of things for you if you let it.  Also,
the MAC suffered from Apple's closed-box policies and the lack of
documentation.  The Amiga has tons of documentation available for the
developer, you can get virtually any piece of information you need.  Though
it has an even steeper learning curve since now a programmer does have to be
careful that when he does a "m = malloc(100)", he doesn't try to then do
a "*(m+150) = 'x'".  An MMU would help you here, even on a singletasking
machine.
>
> Actually, I want an mmu even if I am not multi-tasking!  Before I got
> a Hyperdrive for my Mac, program development consisted of these steps:
>
>       1. Boot machine
>       2. Create ram disk
>       3. Copy System, Finder, and library files to ram disk
>       4. edit/compile/link/program
>       5. Run program
>       6. when program crashes machine go back to step 1
>
> With an mmu, step 6 could have been:
>
>       6. when program tries to crash machine, go back to step 4
>
> which would save a lot of time.

With the exception of 2. (AmigaDOS has an automatic, dynamically sizing
RAMDisk built in), you could easily follow the same cycle on the Amiga.
Depending upon the type of crash, however, you may be given the chance to
cleanly shut down any other processes that are running.  And you always
get to externally debug the system from the monitor if you like.

> --
> "I *DO* believe in Mary Worth"
>
> Tim Smith       USENET: sdcrdcf!ism780c!tim || ima!ism780!tim
>               Compuserve: 72257,3706          Delphi || GEnie: mnementh
--
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Dave Haynie    {caip,ihnp4,allegra,seismo}!cbmvax!daveh

        "I gained nothing at all from Supreme Enlightenment, and
         for that very reason it is called Supreme Enlightenment."
                                                        -Gotama Buddha

        These opinions are my own, though for a small fee they be yours too.
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