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From: tim@ism780c.UUCP (Tim Smith)
Newsgroups: net.micro.mac
Subject: Re: Re: Multitasking Considered Useless?
Message-ID: <3218@ism780c.UUCP>
Date: Fri, 15-Aug-86 21:50:32 EDT
Article-I.D.: ism780c.3218
Posted: Fri Aug 15 21:50:32 1986
Date-Received: Sat, 23-Aug-86 21:52:26 EDT
References: <3150@ism780c.UUCP> <617@cbmvax.cbmvax.cbm.UUCP>
Reply-To: tim@ism780c.UUCP (Tim Smith)
Organization: Interactive Systems Corp., Santa Monica, CA
Lines: 61

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 :-)
>> 
>
>Really?  That's amazing!  The MAC ROM really has support for synchronization
>of separately running tasks, task swapping, task prioritization, intertask 
>signal and message passing, task based exception processing, etc.?  Then
>why do they waste all of their comparatively limited ROM space (actually
>Write-Protected RAM on the Amiga) with these routines if they don't intend
>to use them.  Or are they used by the MAC OS but not accessable to the
>user?  The Amiga starts up tasks for the Workbench, possibly a CLI, the 
>mouse, the keyboard, the disk, the timer, etc. all as a part of normal
>operation.  
>
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.

>
>> But seriously, the problem is not the Mac os.  It is the hardware.
>> Apple was right to not try to put multi-tasking on the Mac.  Without
>> an MMU, multi-tasking is dangerous.
>
>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.

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.
-- 
"I *DO* believe in Mary Worth"

Tim Smith       USENET: sdcrdcf!ism780c!tim || ima!ism780!tim
		Compuserve: 72257,3706          Delphi || GEnie: mnementh