Re: "Real" Multitasking (Re: GNO questions...)

[rwifall@nmsu.edu (Richard J Wifall)]

In article <1993Apr22.015141.3683@vax1.mankato.msus.edu> slp@vax1.mankato.msus.edu writes:

>rhyde@ucrengr.ucr.edu (randy hyde) and bazyar@teal.csn.org (Jawaid Bazyar) are
>confused about the fact that a cooperative multitasking system doesn't need to

        You don't have any clue who Jawaid Bazyar is do you?  If you
would pull your head out of your self-righteous ass (Hi Joe), you might
realize that Jawaid happens to have an extensive background in
multitasking having written both a switcher and a preemptive
multitasking shell. (which is extensive enough for some people to
confuse it with being an OS )

>save as many registers and such during a process switch as a preemptive system
>The reason for this is because a cooperative multitasker only switches during
>function calls, when registers are expected to be nuked anyways.  It would be
>pointless for the task switcher to save registers that the programmer and/or
>compiler are EXPECTING to be changed by the call!

        You seem to forget that not every register gets nuked.  In
fact, most of the registers ARE saved during function calls, (ie
directpage, stackpointer(well, that's kinda obvious :), bank, etc) The
only registers that I generally expect to get nuked are the
accumulator, and data registers.  For instance, a certain preemptive
multitasking shell saves approx 20 bytes of information per process
switch.  Now with a cooperative multitasking, say you don't have to
save x,y,a or possibly the shadowing status.  4 bytes less..  Where
are the extra registers that preemptive has to switch?  I guess they
weren't included on my GS..(or anyone elses for that matter)

>(By the way, I am the author of some BBS software, as well as someone who has
>written both cooperative and preemptive threading programs before. I'm all to
>well aquaited with the problems of implementing transfer protocols, as well as
>multitasking executives.)

        I would venture to guess that Jawaid has a _bit_ more experience
then you in the multitasking arena, and would tend to have a much
higher regard for his opinions.  But then I also trust him so far as
to have bought his program that lets me do preemptive multitasking under
an OS that wasn't meant to support multitasking.


richard@I.think.dereks.post.covered.all.the.other.flammable.material


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