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From: rjc@geech.ai.mit.edu (Ray Cromwell)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: How do we change the scheduler? (Was Re: Multitasking at home...)
Message-ID: <12880@life.ai.mit.edu>
Date: 21 Jan 91 05:09:58 GMT
References: <1991Jan18.231330.16290@Neon.Stanford.EDU> <7553@sugar.hackercorp.com> <1991Jan21.004720.25985@ncsuvx.ncsu.edu>
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In article <1991Jan21.004720.25985@ncsuvx.ncsu.edu> kdarling@hobbes.ncsu.edu (Kevin Darling) writes:
>>> [Mac example: scrolling around while raytracing.]
>
>So the speed diff is only related to the (Mac GetEvent delay x number of
>times) it's called; versus the (Amiga tick routine delay x number of times)
>it's done.  Unless we know those timings, speed claims are meaningless.
>Perhaps there's a better example?  - kevin <kdarling@catt.ncsu.edu>

  A better example of Preemptive vs cooperative multitasking may be
in the continuity of preemptive multitasking. For equal priority
tasks on the Amiga using all of their time-slice, tasks will run at the
same speed. Consider this preemptive cycle chart.

*=Cycle

  Amiga   Time --->
Task A  |********        ********        ********        ********>
Task B  |        ********        ********        ********        >

  Mac   
Task A  |*****               **     ****** *************  **  ***>
Task B  |     ***************  *****      *             **  **   >

  Mac multitasking cycles will be highly irregular in a heavily loaded 
system. I suspect that loading a Mac up with time consuming tasks will make
the system very jerky, while the Amiga will only slow down. (assuming
no high priority tasks block out lower tasks, or something blocks the
display for long periods of time.)

 In my own opinion cooperative multitasking is not multitasking, simply
because its not very transparent. How far do you draw the line in
defining multitasking? Can Commodore 64's considered to be multitasking 
because you can put music, and other programs in the IRQ interupt? Can
I consider a computer to be multitasking, if all software on the system is
written using co-routines to call other software programs?

 Where is the line drawn? I consider the line to be put at preemptive.
Why? Well because I'm considering a task to be an entity which should be
allowed to run without voluntarily giving up its control. Consider a
benchmark. Benchmarks on the Mac vs Amiga may be unfair, because
Mac benchmarks can take all the CPU for its test, while Amiga benchmarks
actually test the system's peformance as a whole. I also don't consider
the Mac to be multitasking since it hasn't been multitasking from the 
beginning.
  Can Mac programs talk to each other? send signals, semaphores? Can they
share files, disc resources? Can the Mac update screen windows that are
behind other windows without bringing them to front?
  The Amiga's OS was designed with multitasking from the start. It contains
all the facilities to support full blown multitasking and sharing of
machine resources.
  Some of the things that make life on the Amiga easier are
Devices, Libraries, and Handlers (all sharable.) On the Amiga, I can
'mount MSH:' and presto, my drive now supports MS-DOS which can be
used with ALL programs. I can also MOUNT NET: and use external
Amiga's devices as if they were my own (yea, yea, AppleTalk can do this too).
I dunno, I guess I'm biased. I've used IBMs,STs, C64/128, Vic20, Trs-80,
Cocos, Macs, and the Amiga is the funnest and best development environment
I've used.