Coop. vs preemptive multitasking (was Re: SwitchItpress release)

[cd248@cleveland.Freenet.Edu (Richard Sherman)]

>Indeed.  MultiFinder is touted as multitasking but that's pushing it a
>bit; without *pre-emptive* multitasking it's still just
>Super-Switcher.  As Scott Anderson (I think) said, it's at the mercy
>of disk drive/SCSI/serial port/etc. access, which is often VERY
>annoying (STUPID PROGRAM! I DIDN'T *REALLY* WANT TO UNSTUFF THAT 20MB
>ARCHIVE!).
 
 
Actually, I thought Multifinder was just a switcher and didn't really
RUN all the programs at once, as opposed to system 7.0.  I could be
wrong about this.
 
Also, what is the big advantage of preemptive multitaksing on a single
user system?  I asked this same question on comp.sys.mac.system and what
it came down to was that cooperative multitasking (system 7.0) only
hands control over to the background programs when the foreground
program is  waiting for user input (most programs spend about 80% of
their time waiting  for user input).  While preemptive multitasking
hands control over after a designated time period.  What makes
cooperative multitasking bad is that a program could hog the cpu if it
weren't written right.  This might be valid for other computers but on a
mac (and a GS I think), control is  given to the background programs
whenever GetNextEvent is called.  The programmer would have to write the
program without using GetNextEvent for it to take over the cpu.
 
I'm not sure what you mean by "at the mercy of disk and serial port
interrupts".  I do know that you can do other things on a Mac with
system
7.0 while your copying files etc.  I also know that it's possible to use
other parts of AWGS while you're downloading a file with its (useless)
communications module.
 
I know preemptive is a better multitasking algorithm but so far I
haven't been convinced that it's the only "real" multitasking.  This
idea seems to have been made up by people trying to sell Amigas.
 

-- 
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| R. Stacy Sherman     cd248@cleveland.freenet.edu or          |
| GEnie: R.SHERMAN2    stacy@uhhacb.uhh.hawaii.edu             |
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