Xref: utzoo comp.sys.atari.st:18404 comp.os.minix:6706 Path: utzoo!attcan!utgpu!watmath!watdragon!dahlia!swklassen From: swklassen@dahlia.waterloo.edu (Steven W. Klassen) Newsgroups: comp.sys.atari.st,comp.os.minix Subject: Re: Multitasking on the ST Message-ID: <15780@watdragon.waterloo.edu> Date: 9 Aug 89 16:10:30 GMT References: <8908021826.AA05333@ucbvax.Berkeley.EDU> <15627@watdragon.waterloo.edu> <652@opal.tubopal.UUCP> <15706@watdragon.waterloo.edu> <666@opal.tubopal.UUCP> Sender: daemon@watdragon.waterloo.edu Reply-To: swklassen@dahlia.waterloo.edu (Steven W. Klassen) Organization: U. of Waterloo, Ontario Lines: 56 In article <666@opal.tubopal.UUCP> alderaan@tubopal.UUCP (Thomas Cervera) writes: >>> If you want to realize reasonable memory segmentation (in my experience this >>>is essential for TimeSharing) you MUST have a MMU. >>Oh really? Then how do you explain the appearance of Minix (a Unix >>look-alike) for the Atari ST? > > But look at the performance of that multitasking system. > And, If I'd decide to write a real nasty program to run under Minix, >the chance is 99% that I crash the WHOLE system with this program. Myself, >I am a Minix user and I think I know what I'm talking about. > > Conclusion : Minix is a very nice software to use it for learning about >time sharing, but it's useless for a *secure* (as I said above) every day >multi(tasking|user) operation because it is definetely not reliable enough. >You WILL have this problem with all multi tasking systems running on an >unmodified ST. "Although MINIX was first implemented on the IBM PC/XT/AT familiy, it was written with portability in mind. We considered it a challenge to test the portability, and used the Atari ST as the target machine for a number of reasons. The ST is a popular machine with a good price/ performance ratio, and attracts a different class of users. The ST uses the Motorola 68000 processor, as several other popular micros do, so that a port to the ST could serve as the starting point for ports to the Apple Macintosh and Commodore Amiga. LASTLY, THERE IS A WIDESPREAD BELIEF THAT UNIX, AND THEREFORE MINIX, REQUIRES THE SUPPORT OF A MEMORY MANAGEMENT UNIT (MMU). PROVING THE OPPOSITE HAS BEEN ONE OF OUR DRIVING FORCES." (excerpt from Intro to Minix ST manual) You emphasize that MINIX ST is not secure and claim this is due to the lack of the MMU. I agree that MINIX ST is not secure but claim that this is not due to the lack of an MMU but due to the fact that Mr. Tanenbaum wanted to keep things simple. To support this note that MINIX is not particularly secure on the IBMs either even though they do have a (sort of) MMU. As for the security of other attempts at multiprocessing (eg. MX2), I have not tried any of them so I really can't comment on them. Finally, I agree with you that the Atari ST hardware is not meant for multitasking. My dissagrement is that I claim this makes multitasking difficult and inefficient (compared to a machine that does support it in hardware) BUT NOT IMPOSSIBLE. Let me close with the conclusion which I have been trying to get accross: 1) MULTITASKING IS USEFUL, EVEN ON A SINGLE-USER MACHINE 2) MULTITASKING IS POSSIBLE WITHOUT A GREAT DEAL OF EXTRA HARDWARE 3) MINIX AND MX2 ARE EVIDENCE THAT ATARI USERS WANT MULTITASKING 4) HENCE ATARI CORP SHOULD GIVE US MULTITASKING *WITH*THE*HARDWARE*TO* MAKE*IT*EFFICIENT. Steven W. Klassen Computer Science Major University of Waterloo