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From: braner@batcomputer.UUCP
Newsgroups: comp.sys.amiga,comp.sys.mac,comp.sys.atari.st
Subject: Re: Re: Mac vs. Amiga (vs. ST)
Message-ID: <2174@batcomputer.tn.cornell.edu>
Date: Mon, 2-Feb-87 00:07:30 EST
Article-I.D.: batcompu.2174
Posted: Mon Feb  2 00:07:30 1987
Date-Received: Tue, 3-Feb-87 18:54:02 EST
References: <8392@watrose.UUCP> <1314@cbmvax.cbmvax.cbm.UUCP>
Reply-To: braner@batcomputer.UUCP (braner)
Organization: Theory Center, Cornell University, Ithaca NY
Lines: 27
Summary: THAT is NOT multi-tasking...
Xref: watmath comp.sys.amiga:1867 comp.sys.mac:1109 comp.sys.atari.st:1237

[]

In the Atari ST (or the Mac, as far as I know) there is NO polling of the
keyboard (nor the mouse):  They are INTERRUPT-DRIVEN.  Since it takes
very little time to process the incoming keystrokes relative to the
time in-between keystrokes, that does not degrade performance.  And
it has absolutely nothing to do with multi-tasking.  Beyond that, the
ST (or GEM, rather) has a "limited multi-tasking kernel" which lets
one 'application' and several 'desk-accesories' (in other words, several
programs) run simultaneously, each being reactivated when a message is
addressed to it (e.g. a keystroke or a mouse click), but not bothered
when not necessary.

As for background reading of the disk:  Usually a program NEEDS the data
it requested from the disk drive BEFORE it can do anything else, so
no amount of multi-tasking will speed that program up while it's waiting.
On the other hand, SOME specially-designed programs sometimes read the
disk BEFORE the data is needed, i.e. invite an overlap of reading the
disk and some other processing.  On the ST that is possible too, since
the disk I/O is done via the DMA chip, which (as far as I know) CAN take
a command and then execute it independently.  It does steal CPU memory
cycles for that, though (or does it? experts, step up?).

- Moshe Braner

PS: I am just trying to clarify the notion of "true multi-tasking",
and NOT to continue religious wars about which machine is better.