Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!decwrl!apple!daveo
From: daveo@Apple.COM (David M. O'Rourke)
Newsgroups: comp.sys.mac.system
Subject: Re: PPC, IAC, and True Multitasking (tm)
Message-ID: <44150@apple.Apple.COM>
Date: 22 Aug 90 00:27:05 GMT
References: <1990Aug3.040513.14844@d.cs.okstate.edu> <2760@bridge2.ESD.3Com.COM> <13888@cbmvax.commodore.com> <3474@tellab5.tellabs.com> <6588@milton.u.washington.edu>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 31

kraig@biostr.biostr.washington.edu (Kraig Eno) writes:
>A workstation like the NeXT will do this sort of thing.  Now, I've never
>used a window system on ANY Unix machine that is as responsive as
>Multifinder, but the Mac is NOT multitasking.

  There are several example of multitasking system that aren't pre-emptive.
Lots of early computer OS's did the context switch off of some/all system
calls or other non-preemptive mech.  I've yet to find an OS book that doesn't
mention co-operative multi-tasking as a scheduling mech.

  Multi-tasking _STRICTLY_ defined is the running of more than one process
at a time.  Well to do that you need a CPU for each process.  So any single
CPU system is not a multi-tasking system.  Or when ever you get n+1 processes
going on an n-processor system then you no longer have a multi-tasking
system.

  This must be the about the 100th time I've been drawn into this debate. Seems
to happen about every three months.  Multi-tasking as defined by most OS books
is the ability to schedule the processor to do more than one thing without
the current process running to completion.  Multi-finder saves and restores
context, and does do some limited scheduling of the processor resource.
Therefore multi-finder is a multi-tasking extension of the Macintosh OS.  Just
because the scheduling method doesn't do it the way most bigger OS's do it
doesn't remove the ability.

  There is more than one way to multi-task a system, and there will always be
debate regarding which way is best.
-- 
daveo@apple.com                                               David M. O'Rourke
_______________________________________________________________________________
I do not speak for Apple in *ANY* official capacity.