Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!amdahl!chuck
From: chuck@amdahl.uts.amdahl.com (Charles Simmons)
Newsgroups: comp.arch
Subject: Re: Survey of architectures was (Re: Proposed architecture characterization)
Message-ID: <29301@amdahl.uts.amdahl.com>
Date: 22 Apr 88 04:36:15 GMT
References: <2048@gumby.mips.COM> <10504@steinmetz.ge.com> <7657@ames.arpa> <21883@bu-cs.BU.EDU>
Reply-To: chuck@amdahl.uts.amdahl.com (Charles Simmons)
Organization: Amdahl Corporation, Sunnyvale  CA
Lines: 67

In article <21883@bu-cs.BU.EDU> bzs@bu-cs.BU.EDU (Barry Shein) writes:
>
>Although the ultimate machine/os/language/etc which can be used as a
>universal standard is an attractive idea it remains a dream, quite
>possibly a false one, it applies the wrong assumptions.
>
>Computers exist within a techno-economic framework. Why doesn't
>someone build the ultimate frob panel that will work as well for an
>oscilloscope as a microwave oven or synchrotron? Is this a reasonable
>question?
>
>So far the purpose of computers is to simulate other realities. As the

I think Barry has some good points here, and I particularly
like the sentence "The purpose of computers is to simulate
other realities".  I think I have small disagreements with some
of his comments, however.  

First, I would question whether the original poster really
cares about having a single machine implementation and a single
instruction set.  My claim is that most people are not directly
exposed to these aspects of a computer system and that they
could really care less.

Next I would ask, is it really the case that the purpose of
an operating system and a language is to simulate realities?
My response would be "no".  The purpose of an operating system
is to manage and allocate the resources of a computer among
various requesting processes.  The purpose of a language is
to allow a person to specify the other reality that she wants
the computer to simulate.  I see no inherent reason why standard
versions of an operating system and language cannot and should
not exist, except for the fact that no one has yet designed
the perfect OS and language.

>technological understanding and economics of the desireability of
>having simulations of these realities changes computer architectures
>change. New opportunities arise and they are largely economic. For
>example, address spaces imply real wires and fighting combinatorial
>connectivity problems which cost real money, a group of people have
>trouble agreeing on the maximally needed address space. One person
>says that enough bits to address every electron in the universe should
>be enough, another points out the computational convenience of a
>segmented, sparse address space. Another notes that you will need at
>least one more bit to store the spin of each electron, another bunch
>to store its location or energy level. Another says that is not
>worthwhile...
>
>Put another way, no one has successfully described a set of operations
>both sufficient and minimal with which to describe reality. It's like
>asking why we come up with new words in human languages, it's because
>new ideas need to be expressed.

We don't need to describe a sufficient set of minimal operations
to describe all possible realities in order to produce a standard
OS and language.  These tools should be sufficiently powerful
that each individual could use these tools to define their own
realities.  

Of course, this leaves open the question of things
like having a standard set of device drivers, or a standard
set of subroutine libraries.  It would be nice to have standard
*sub*sets of these things.

>	-Barry Shein, Boston University

-- Chuck Simmons