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From: rbl@nitrex.UUCP ( Dr. Robin Lake )
Newsgroups: comp.sys.amiga,comp.sys.mac
Subject: Re: Defense of multi-tasking response
Message-ID: <522@nitrex.UUCP>
Date: Fri, 21-Aug-87 10:20:14 EDT
Article-I.D.: nitrex.522
Posted: Fri Aug 21 10:20:14 1987
Date-Received: Sun, 23-Aug-87 10:38:23 EDT
References: <407@cc5.bbn.com.BBN.COM>
Reply-To: rbl@nitrex.UUCP ( Dr. Robin Lake )
Organization: The Standard Oil Co., Cleveland
Lines: 43
Xref: mnetor comp.sys.amiga:7655 comp.sys.mac:5866

In article <407@cc5.bbn.com.BBN.COM> denbeste@cc5.bbn.com.BBN.COM (Steven Den Beste) writes:
>
>> Now some substance: Most time-slice mutlti-tasking operating systems
>> guarantee that every ready-to-run job will get a chance to run, at
>> least once a time-interval (often a second.) This has the effect of
>> slowing down interactive performance: the interactive application
>> doesn't get all of the processor, so there is a lag in its response to
>> user input.
>
>OK, I don't like "my computer can beat up your computer" discussions any more
>than anyone else, so I will confine myself to theoretical discussions. First I'd
>like to point out that when multi-tasking, not every job is actually
>run-bound.

.....
Excellent discussion of task-switching resource sharing eliminated for 
brevity ....

What Steve describes reminds me of the histories of both DEC and IBM
operating systems.  (Please excuse any errors of an ageing mind! :-} )
DEC originally had RSX-11-A, about 800 bytes of priority task-sharing
control that managed well-behaved memory-resident programs.  Then followed
enhancements that allowed memory protection, programs called from disk,
checkpointing, and maybe even not-well-behaved programs.

IBM went along much the same path, from a single job run to completion, to
multiple jobs in memory, each in a fixed size partition, to
operator-controlled memory partitions, to dynamic allocation.  MVS even
today looks a lot like a fast batch processing stream to the user.

If we extrapolate from history, perhaps the Mac will proceed along the
same lines.  Sure, some additional memory management hardware might be
needed, but at least the box is open now!

Rob Lake
(It's really BP America Research, Development and Technical Service now)
decvax!mandrill!nitrex!rbl

>     Steven C. Den Beste
>     Bolt Beranek & Newman, Cambridge MA
>     denbeste@bbn.com  (ARPA or CSNET or UUCP)
>     harvard!bbn.com!denbeste (UUCP)
>