Path: utzoo!attcan!uunet!samsung!usc!bbn!drilex!dricejb
From: dricejb@drilex.UUCP (Craig Jackson drilex1)
Newsgroups: comp.arch
Subject: Re: Single user vs. shared (was Re: Killer Micros and vectorized code)
Summary: It's all relative
Message-ID: <9208@drilex.UUCP>
Date: 20 Mar 90 13:57:02 GMT
References: <51771@lll-winken.LLNL.GOV> <100598@convex.convex.com> <52661@lll-winken.LLNL.GOV> <1990Mar18.023523.4034@ultra.com> <52817@lll-winken.LLNL.GOV> <53714@bbn.COM>
Organization: DRI/McGraw-Hill, Lexington, MA
Lines: 25

Many of the participants in discussion of shared computers vs single-user
computers seem to believe that there is an absolute answer.  However,
it's really a tradeoff involving the cost of redundant (possibly idle)
equipment, the cost of switching use, and the cost of being denied use
due to others using the equipment.  "Expensive" things will be shared,
whether they are computers or pieces of lab equipment.  Expensive can be
measured by comparing the cost of obtaining extra, possibly idle equipment
against the opportunity cost of waiting to use the shared equipment.
The ability of computers to switch from one task to another tends 
to reduce the opportunity cost of having to share it.

The amount of computing resources we have been willing to devote to a
single user has been rising for many years.  At one time, even the I/O
devices were shared-use: printers, card readers, keypunches.  Later,
it was found useful to devote a teletype to a user for extended periods
of time (time-sharing sessions).  Still later, it became common to
give an 8080-class computer (buried in a terminal) to each user.  Now,
we are discussing whether general-purpose workstations or X terminals
are the proper paradigm for users.  Yet most X terminals have a good deal
more computing power than the single-user workstations of 5 years ago,
and the shared-use computers of 15 years ago.  The difference is the cost.
-- 
Craig Jackson
dricejb@drilex.dri.mgh.com
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