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From: rej@cornell.UUCP (Ralph Johnson)
Newsgroups: net.micro
Subject: Re: IBM vs VAX/unix
Message-ID: <6683@cornell.UUCP>
Date: Fri, 2-Mar-84 10:22:39 EST
Article-I.D.: cornell.6683
Posted: Fri Mar  2 10:22:39 1984
Date-Received: Sat, 3-Mar-84 22:05:51 EST
References: <571@pucc-h>
Organization: Cornell Univ. CS Dept.
Lines: 51

Microcomputers CAN replace most uses of VAXen.  Not all, of course, and
I wouldn't want to replace a VAX with any number of PCs, but there are
much more cost effective ways to provide VAX equivalent power than with
a VAX.  68000 Unix systems are surprisingly powerful.  I judge the Callan
Unistar-100 to be about one fourth the speed of a VAX11/780 for long
compiles.  It is about 60% of a VAX for non-floating point computation
intensive tasks.  A 68000 with 2 or 4 Meg of memory is probably the cheapest
way to run Lisp.

The major problem with microcomputers is slow, small disks.  The speed ratio
of applications on the Callan to those on the VAX depends primarily on the
amount of disk accesses that they require, since the Callan uses slow 5"
winchesters.  Given a fast network with large file servers, 68000s could
compete with VAXen in every application that does not use floating point.

The major advantage that microcomputers have is that each user can have his
own machine.  Every VAX user knows the "it's two in the afternoon and the
load factor is too high" blues.  A VAX may beat a Callan at 7 AM, but a
Callan will get my job done faster at 3 PM.  While one nroff job saturates
a VAX, it takes 10 nroff jobs to saturate 10 microcomputers. (And the jobs
will probably finish two to four times as quickly.)

Two dozen VAXen with disks and other peripherals cost on the order of 2 to 5
million dollars.  For two million dollars you can get 200 Callans at single
quantity prices - the quantity discount will buy an ethernet and some file
servers.  A VAX can support any number of people if they are not doing
anything, but even two or three nroff jobs will slow it markedly.  Thus, if
people are doing heavy computation, ten 68000 systems will provide more
throughput and better response time for a VAX, for less money.

Notice that I do not necessarily think that 68000s are the best micro or that
Callan makes the best 68000 Unix computer.  However, I do think that these
alternatives provide more Unix power for the dollar than a VAX, thus any
argument that some other micro is even more cost efficient is further
argument for my case.

One reason to get a VAX is to use some special piece of equipment or
software.  Eventually, array processors and graphics equipment will be
interfaced to microcomputers, and the software will get ported to 68000s.
For example, I said that 68000s were a more cost effective way to run Lisp
than VAXen, but the various 68000 Lisp systems seem to be in various stages
of being ported from the VAX right now; I don't know of any which is supposed
to be ready for production use.

A major problem with connecting lots of microcomputers together is that it
requires lots of unwritten software.  SUN is supposed to have a complete
system soon, and there are a few systems like Appolo which are finished, but
quite expensive.  However, everything that I have said is true in theory, if
not in practice.

Ralph Johnson  rej@cornell    cornell!rej