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From: jpenne@ee.ualberta.ca (Jerry Penner)
Newsgroups: comp.sys.apple2
Subject: Re: Multitasking on a II
Message-ID: <1990Dec11.004650.8077@ee.ualberta.ca>
Date: 11 Dec 90 00:46:50 GMT
References: <10395@ucrmath.ucr.edu> <2433@unsvax.NEVADA.EDU> <10425@ucrmath.ucr.edu> <14705@smoke.brl.mil>
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Organization: University of Alberta Electrical Engineering
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In article <14705@smoke.brl.mil> gwyn@smoke.brl.mil (Doug Gwyn) writes:
>In article <10425@ucrmath.ucr.edu> rhyde@ucrmath.ucr.edu (randy hyde) writes:
>>All you need to do multitasking on a II is a timer interrupt.
>>...  To truely implement multitasking on the II you need either
>>memory management or specially written applications.
>
>This is simply not true.  Timer interrupt is needed only for preemptive
>scheduling, but multitasking does not have to be preemptive.  Memory

Non-preemptive multitasking is not much fun.  Especially since we have zillions
of programs out there for the GS & other IIs that know nothing about it.  They
would never give the CPU back.  Pre-emptive multitasking is VERY desireable.

>management offers protection for one task against bugs in another, but
>this is more a convenience than a necessity.
		^^^^^^^^^^^^       ^^^^^^^^^

Not quite.  Maybe if you only write your own software or can afford to have
some other program crash another one.  It is a necessity when reliability is
considered.  And it sure makes life a LOT easier for software developers.
This must be taken into account when designing a system.  Otherwise, only a
few will write for it.

>The terminal I am typing this on is truly multitasking, and it uses
>neither timer interrupts nor memory management.

-- 
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	Jerry Penner		...!alberta!bode!jpenne