🚀 go-pugleaf

In article <1066@philmds.UUCP> leo@philmds.UUCP (Leo de Wit) writes:
>In article <471@tw-rnd.SanDiego.NCR.COM> johnl@tw-rnd.SanDiego.NCR.COM (John Lindwall) writes:
>|Amen to that! Amiga owners have suffered with the lack of an MMU.  The
>|usefulness multitasking is a given, IMO.  The security of Amiga's multitasking
>|is poor due to the lack of memory protection supplied by an MMU.  Those of
>|you who agree multitasking is useful, and would like to see it on an Atari:
>|Demand it from Atari and demand MMU support as well.

>
>I think two issues are being confused here, the need for per process
>memory protection, and the possible to run processes 'simultaneously'.
>Why should memory protection be a hotter item when parallel processes
>are involved?

Because of the potential for a single user program to cause the termination
of all the processes in the system.

Consider: You are a user of the Spiffy multi-tasking-but-no-
per-process-memory-protection Machine.  You fire up a ray-trace.  It'll
finish in 12 hours so you start up a terminal program and download some cool
PD software from a BBS.  While thats all going on "in the background",  you
fire up your compiler and start writing a new program.  You run your program
and it has pointer error which causes random data to scribbled across memory.
The machine crashes --- badly -- all of the processes on the machine terminate
and the system reboots.

On a machine with memory protection (OK and resource tracking) the MMU will
prevent corruption of other processes address space, and the nasty process can
be removed from the system cleanly.


> In the current situation it is just as well feasible for
>instance by an application program to thrash the space of the shell it
>was invoked by. So if you insist on security, you should insist on it
>right now already.
>

I'm all for system robustness for ANY system.  My point is that when you
introduce multitasking, memory protection is more important due to the
potential to disrupt other processes.

>An MMU alone probably won't hack it; you will probably want a 680x0
>(x >= 1) to be able to page in new memory (a 68000 doesn't maintain
>enough internal information to be able to restore correctly from a
>BUSERR).
>
>   Leo.

Sounds Good!  But now you're wandering into the area of virtual memory and
that's not what our original discussion was about.  Thanks for the reply.


----------------------------------------------------------------------
John Lindwall                            johnl@tw-rnd.SanDiego.NCR.COM
           "Above opinions are my own, not my employer's"
   Health is merely the slowest possible rate at which one can die.