Path: utzoo!attcan!uunet!jarthur!nntp-server.caltech.edu!tybalt.caltech.edu!toddpw
From: toddpw@tybalt.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.arch
Subject: Re: Macintosh OS
Message-ID: <1990May28.083518.26003@laguna.ccsf.caltech.edu>
Date: 28 May 90 08:35:18 GMT
References: <402@newave.UUCP> <3300131@m.cs.uiuc.edu> <5031@quanta.eng.ohio-state.edu>
Sender: news@laguna.ccsf.caltech.edu
Organization: California Institute of Technology
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JONESD@kcgl1.eng.ohio-state.edu (David Jones) writes:

>If Apple's OS is very close to Lampson's ideal, then Lampson's model is flawed.
>The primary complaint against Macintosh OS is the lack of true multi-tasking,
>Lampson's ideal environment is only suitable for single-tasking use.

I think you're confusing single/multi-tasking and single/multi-USER.

>Multi-tasking requires that use of system resources, such as memory and
>I/O devices, must be coordinated.  The cooperative approach doesn't work it
>pratice, a protected kernel with time-slicing and tighly defined device
>interfaces does.

Cooperative multitasking is excellent for single user environments because the
"foreground" process can always offer the best response time. Scheduling is not
much of an issue, but there are extra burdens on the programmer and that is the
real problem that Apple ought to deal with.

In a Multi-user environment it is absolutely essential that each process be
isolated, preferably by the hardware. Pre-emptive multitasking is also required
to insure that everyone gets CPU time, but that makes response time very hard
to guarantee.

We're looking at two ends of a stick, people. Both Apple's O/S and Unix are
capable of multi-tasking in a practical sense (meaning that you can have more
than one program in the machine and running simultaneously from the user's
point of view -- heck, an Apple IIgs can do _that_). But the Mac O/S is a lot
more responsive to one user and a Unix box is reasonably responsive to a group
of users.

It's darned hard to get both response time a reliable multi-user operation in
the same box. That's where things are headed, but don't criticize a stepping
stone because it isn't the whole bridge.

Todd Whitesel
toddpw @ tybalt.caltech.edu