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From: guy@sun.uucp (Guy Harris)
Newsgroups: net.arch
Subject: Re: VERY LARGE main memories
Message-ID: <7078@sun.uucp>
Date: Tue, 9-Sep-86 14:18:29 EDT
Article-I.D.: sun.7078
Posted: Tue Sep  9 14:18:29 1986
Date-Received: Wed, 10-Sep-86 01:30:50 EDT
References: <1645@ames.UUCP>
Distribution: net
Organization: Sun Microsystems, Inc.
Lines: 61

> Gawd, you guys on the net!  Come on!
> 
> So VAX/Unix oriented, so blinded!

Oh, come off it.  You damn well know that most machines out there,
regardless of whether they run UNIX or are VAXes, are byte-oriented.  The
use of "byte" when talking about memory sizes has *NO* relation *WHATSOEVER*
to a VAX or UNIX mindset.

> The Cray is a word oriented machine.  Take out the factor of 8 from all
> of your calculations.  You can tell a person's thinking by the words they
> choose.  The Cray-2 is a 256 MW not a 2 GB machine.  These are not the same
> because the conversion is non trivial.

Why?  Does the Cray-2 store characters one per word?  Does it store
*everything* one per word?  Even if it does, that isn't enough to recommend
that "word" be used in a general discussion of large main memories.  "word"
is a *useless* term for general discussions of memories, because it means a
different amount of memory on different machines.  This discussion is NOT a
discussion of the Cray-2, it is a discussion of large main memories.  As
such, the byte is the appropriate unit to discuss, since it is the same size
on almost all machines out there.

> Crays are word oriented machines.

You already said that.  Merely stating this twice doesn't make it more
interesting.  Explain *why* this renders discussion of Cray memory sizes in
bytes inappropriate.  The PDP-10 is a word-oriented machine also; however, a
9-bit byte is a *very* appropriate unit for comparative discussions of
memory size, since one (9-bit) byte holds a character (which can be
addressed independently given a byte pointer), four bytes holds an integer,
(byte) pointer, or single-precision floating-point number, and eight bytes
holds a double-precision floating-point number - just like the VAX.  The
available range of values of these types are different from that on a VAX,
but the difference is not enough to make a difference in gross discussions
of memory sizes.

> Anyone who says "2 GB" is showing a great deal of naive.

That's "naivete", modulo various diacritical marks, and this statement
needs a lot more defense than you've given it.  If the problem is that a
given data structure (tree, 2D array of floating-point numbers, etc) takes a
different amount of memory on a Cray-2 than on another machine, then the
appropriate unit in the discussion is *NOT* words, it's elements of said
data structure.

> Get off your VAXen an try Univacs (36-bit), IBM's inverted bit order,
> and other systems.

"*BIT* order"?  What relevance has that?  I presume you meant "*byte* order,
in which case which "inverted byte order" do you mean?  The byte order on
the IBM PC is the same as that on the VAX, and I could see some future
80386-based IBM machine having lots of main memory.  The 360/370 family, by
the way, is byte-oriented and memory sizes are given in bytes....

Your assumption that the use of "bytes" in this discussion is an indication
of VAX/UNIX tunnel vision is way off the mark.
-- 
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com (or guy@sun.arpa)