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From: news@cit-vax.Caltech.Edu (Usenet netnews)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Mainframe vs Micro
Message-ID: <1415@cit-vax.Caltech.Edu>
Date: Sat, 3-Jan-87 16:45:32 EST
Article-I.D.: cit-vax.1415
Posted: Sat Jan  3 16:45:32 1987
Date-Received: Sat, 3-Jan-87 21:53:30 EST
References: <657@imsvax.UUCP>
Reply-To: tim@tomcat.UUCP (Tim Kay)
Organization: California Institute of Technology
Lines: 96
Summary: PC's have a long way to go

Organization : California Institute of Technology
Keywords: 
From: tim@tomcat.Caltech.Edu (Tim Kay)
Path: tomcat!tim

In article <657@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes:
>
>There are several points to consider concerning the mainframe/micro question
>as it relates to databases.  The 32 meg limit doesn't apply to Novell Netware.

You are totally in the wrong ball park.  PCs aren't going to encroach on
mainfames just because the 32M limit was broken.  A _typical_ drive that
IBM sells (3380) has about 600 Mbytes on it.  A _typical_ machine they sell
will have anywhere from 10 to 500 of these drives on it.  A PC can handle
only two drives.  One of the main concerns in designing the XA architecture
at IBM was that installations were running out of address space for numbering
devices (disks, tape drives, terminals, CTCAs, etc.).  The old 370
architecture can handle 4,096 devices!  The new XA architecture can handle
significantly more.

Typically, a single machine configured as above is not adequate, so IBM
offers (and has offered for about a thousand years now) the ability to
network these large machines.  There are installations that have dozens
of the machines (of the size I just mentioned) networked together.

Consider that an IBM mainframe handles all of its I/O through I/O channels.
These are really separate computers that have direct access to memory and
run simple programs that the main CPU constructs for them.  Each channel
on an IBM mainframe at least as powerful as an 80386.  A mainframe has
many channels for each CPU.

>I've seen 750 and 780 VAXs destroyed by fewer than 30 people doing database
>work (or attempting same) at the same time.  The PCs are faster and better.

A Vax 780 is a wimpy machine that was not designed for large tasks.  Clearly
PCs are encroaching upon DEC mainframe type sales.  Actually, it is incorrect
to call DEC machines mainframes.  The term they coined for them is, I believe,
"supermini."

The present discussion started when a claim was put forward that PCs are cutting
into IBM's mainframe market.  DEC offers no machine that is anywhere near the
power of IBM's mainframes.  IBM can _routinely_ put hundreds of terminals
on a single machine, and it will perform well.  Just try to network more than
a few tens of PCs.

>The PC revolution, like our free-market system as opposed to communism, takes
>human nature into account, at least as it applies to bosses and managers.
>I've never yet seen one of these who, upon hiring three new people to work
>on a multi-user computer system, didn't simply add three new terminals to 
>the system.  With PC networks, they are forced to add three new computers
>to the system.  And the beauty is that they do so with smiles on their faces,
>since PCs have gotten to the point of being cheaper than most mainframe
>terminals anyhow.

This argument doesn't fly.  Quite often, PCs are used as terminals for
IBM (and DEC) mainframes.  It requires the simple addition of an IRMA
or PCOX type card, which costs about the same as an Ethernet card.
The only disadvantage in using PCs is that the screens are two small.  IBM
sells a terminal that can have four windows on it, each of which is
(I believe) 132 characters by 25 lines.  Alternatively, the same terminal can be
used for one huge window.

I will rephrase a statement that I made earlier.  Most people have absolutely
no idea what the bulk of the computing power in this country is used for.
They see what is being done on PCs and Vaxes, and they see lots of them.
They assume that this type of computing is typical.  It is not.  You could
probably take all the Vaxes in the world, multiple by 100, and you would
not have enough computing power to replace all the IBM mainframes in the
world.

Every year, IBM's profits are roughly equal to DEC's SALES.

None of this discussion starts to consider machines like Crays or IBM
3090s with vector processors.  They can compute thousands of times
faster than a PC.  An 8087, for example is about 5 kiloflops.  A
68881 is about 30 kiloflops.  A Cray XMP 48 (by now an old machine)
was about 1 gigaflop.  This is a factor of 1,000,000,000 / 30,000 ,
= 33,000 difference in performance.

In conclusion, I'd like to suggest that a PC is to a mainframe like a
rubber raft is to a yacht.  They both have their uses, and many
people that have yachts have uses for rubber rafts.  Likewise, many
people that can't afford or justify yachts can afford and do enjoy
rubber rafts.  On the other hand, it is ludicrous to think that,
because rubber rafts are becoming less expensive, the sales of yachts
are falling off.

Comments?

Tim
Caltech

Timothy L. Kay				tim@csvax.caltech.edu
Department of Computer Science
Caltech, 256-80
Pasadena, CA  91125