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From: ckp@grebyn.com (Checkpoint Technologies)
Newsgroups: comp.sys.amiga
Subject: Re: Multifinder - Just the Facts, man.
Message-ID: <19991@grebyn.com>
Date: 3 May 90 23:30:58 GMT
References: <20499@boulder.Colorado.EDU> <8930@hubcap.clemson.edu> <10143@sdcc6.ucsd.edu> <43785@iuvax.cs.indiana.edu> <7416@wehi.dn.mu.oz> <1990May3.042500.18758@wam.umd.edu>
Reply-To: ckp@grebyn.UUCP (Checkpoint Technologies)
Organization: Grebyn Timesharing, Vienna, VA, USA
Lines: 51

In article <1990May3.042500.18758@wam.umd.edu> ddev@wam.umd.edu (Don DeVoe) writes:
>In article <7416@wehi.dn.mu.oz> BAXTER_A@wehi.dn.mu.oz writes:
>>Youre right, Andy.
>>This drongo doesn't know the difference between multitasking and parallel
>>processing.
>
>Tell us, just what is the difference? In a strict sense, you can't have
>(true) multitasking without multiple processors...anything else is just
>program swapping; multitasking is implicitly denied in a single processor
>system. And just what is a drongo, anyway?

It's all a question of semantics.  As far as I understand:

"Parallel processing" has come to mean more than one CPU of like
architecture cooperating to solve a single job.  Several linked
Transputers may be considered "parallel processing" if they are
cooperating to run one program (which typically Helios doesn't do I
understand).

"Multi-tasking" is when a single CPU is shared among several jobs, each
of which has a current "context" which is preserved by the OS,
by whatever means.  By this definition I consider Multi-Finder
"multi-tasking", but before you flame me, read on...

"Pre-emtive" multi-tasking means that the single CPU can be taken
from one job to another at any arbitrary point in the first job;
it happens that the Amiga has Exec functions to disable and enable
pre-emption (Forbid and Permit), but most pre-emptive multi-tasking
OS'es don't, they use semaphores.

"Co-processing" and "Co-processors" indicate multiple processors of
dislike architectures; usually each co-processor is designed to
handle a particular kind of work efficiently, like floating point
math, IO tasks, or graphics, and may not be powerful enough to be
considered general-purpose CPUs, but they might.  The Z80 in the A2090
and the 6502's in the Max IIfx would be co-processors. I guess I don't
consider a simple DMA channel as a co-processor, though some may not
agree with me.

OK, that means the Mac with Multi-finder is *not* parallel processing,
*is* multi-tasking but *not* pre-emptive, and *may* have co-processors
if you pay enough (the IIfx, the 8/24 GC color card, and the 68881/2
math chip).

The Amiga is *not* parallel processing, *is* pre-emptive multi-tasking,
and *does* have co-processors and DMA.
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