Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!csun!kithrup!sef
From: sef@kithrup.COM (Sean Eric Fagan)
Newsgroups: comp.arch
Subject: Re: How wrong is MS-DOS? (or: Tools Tools Tools)
Message-ID: <1991Jan13.053112.22995@kithrup.COM>
Date: 13 Jan 91 05:31:12 GMT
References: <EGDORF.91Jan12184630@zaphod.lanl.gov> <11255@lanl.gov>
Organization: Kithrup Enterprises, Ltd.
Lines: 39

In article <11255@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
>No. Piping things together is about the _least_ efficient way of
>incorporating a functionality into a tool.  Almost _anything_ is
>an improvement.  

Actually, pipes can be an improvement for sequential processing, since,
while the one process is waiting on I/O, the other process can be
processing.  Throughput is increased as a result.

>In the modern sense of the term, UNIX doesn't provide multitasking
>either.  It provides multiprocessing.  Pipes are a weak subset of
>the general concept of interprocess communication.

Uhm, Jim, you've got your terms reversed.  Multiprocessing is generaly used
to mean multiple processors; multitasking means just that:  multiple tasks.
Now, it's true, unix is not *really* multitasking, as, in most
implementations, only one task runs at a time (but not necessarily; for
example, in a PC, with a smart serial card, the serial card can run in
parallel with the CPU).  Note, however, that, if you want to say that unix
isn't multitasking, you have to say it's not multiuser, either (since only
one user is using the machine at a time).  This is true of most machines,
however.

Now, about unix and multiprocessing:  every major unix vendor these days has
a multiprocessing version of unix available, if a multiprocessor version of
the hardware is available.  Crays, for example, under unicos; AT&T, with the
3b6000 (is that the number? I really forget); SCO, with MPX and something
like 5 or 6 different hardware vendors; Sequent, Encore, ETA, Elxsi, MIPS,
DEC, etc.

Note that, with multiple processors, you get the advantage in speed, if you
use pipes, without having to change code in any way, as different parts of
your "program" can run in parallel.

-- 
Sean Eric Fagan  | "I made the universe, but please don't blame me for it;
sef@kithrup.COM  |  I had a bellyache at the time."
-----------------+           -- The Turtle (Stephen King, _It_)
Any opinions expressed are my own, and generally unpopular with others.