From: utzoo!decvax!microsof!uw-beaver!cornell!vax135!floyd!harpo!seismo!rlgvax!guy
Newsgroups: net.micro
Title: Re: Re 8086: Good thing come in
Article-I.D.: rlgvax.311
Posted: Thu Apr 21 18:18:31 1983
Received: Sun Apr 24 05:54:22 1983
References: ncsu.1189


    Its funny how hardware technology influences peoples thoughts of what
    is "good".  Unix was born and nurtured on a limited address space cradle
    of 64k bytes.  Did that environment produce a criple?  No.

Nobody said it was a "cripple" (two "p"s, please).  There are some applications
that REQUIRE more than 64kB of data/stack and/or 64kB of code.  Why did
Zilog have a segmented version of their chip?  Why did Motorola and National
Semiconductor come out with a chip with a large address space?  Why, for
that matter, did *Intel* provide some (not great, but some) support for 32-bit
pointers on the 8086?  Why did DEC come out with the VAX?  And so on.

    Rather it produced the so called "UNIX Style", of a minimal OS kernal,
    and collections of small useful programs which the OS could "connect"
    at run-time.  These ideas are generally accepted as good, independent
    of any cpu architecture.

They are, indeed, good ideas; HOWEVER, NOT every application can be written
that way!  Why have some many other operating systems implemented overlaying
and virtual arrays?  Why have so many people added overlaying to PDP-11 UNIX?

    Indeed, one need merely look at OS/370 and the
    s/370 architecture to see that the ideas are not a direct result of the
    address space limits.  The s/370 operates most of the time in a world
    of 12 bit addressing -- all that will fit into the 12 bit displacement
    field.  More expansive addressing requires trick use of address constants,
    arithmetic, multiple base registers and all manner or other stuff.  Did
    this result in the "UNIX Style"?  Is OS/370 a minimal kernal?  Are OS
    programs typically small, sleek and robust?

    Comments about the strangling confines of the 8086 are a load of ____
    disguising the deep down lack of understanding or faith in the UNIX
    style.  Sure its nice to have a zillion byte address space. Sure that
    makes it easier to address a 200K array. (Funny, I've never used one.)
    Sure tis easier to have a magabyte process image. I'd rather have a
    set of smaller, cleanly interfaced programs which are "linked" at run
    time by the OS, then a big lumbering OS/370 "subsystem".

Bull____, to put it bluntly.  Many, if not most, of us have PERSONAL EXPERIENCE
of programs which suffer greatly in being confined in a small address space.
Take PDP-11 INGRES.  (Sorry, no Henny Youngman lines here.)  It was composed
of 7 processes which communicated through pipes.  It seems that the UNIX style
didn't fit INGRES very well.  The VAX-11 INGRES is faster, and much of that
is due to the fact that it is *one* process.  The fact that YOU have never
used a 200K array doesn't mean that NOBODY uses them; I wrote some scientific
programs on a PDP-11 on RT-11, and I had to overlay them up a blue streak in
order to get them to fit.  The "UNIX style" (if people start thinking that
ALL UNIX programs MUST be written in that style, a lot of the UNIX market
will dry up and blow away) works great IF the program divides neatly along
multiple-process lines.  Scientific data analysis frequently, for example,
doesn't.  I'm sure the people from Sun can give many more examples of
applications that are a LOT happier if they don't have to contort to fit a
limited address space.  I have faith that the UNIX style works with applications
that it works with.  I have written my share of clean "UNIX-style" programs,
so I resent the implication that I am a Philistine who can't do so.

    Lets all have a moment of silence for the passing of the thing that
    brought UNIX into the world and nurtured its early philosophy. And
    give thanks that K.T. and D.R. didn't have a 68000 15 years ago.

I hate to disappoint you, but I believe D.R.'s current machine is (oh apostasy)
a VAX-11/780.  Should Dennis put on the hairshirt, pick up the sackcloth and
ashes, and do penance for daring to question the wisdom of using machines with
a small address space?  If UNIX can't advance with technology, I suspect it
really couldn't be called a good modern operating system.  However, the fact
that it has adapted to small single-user machines, workstations like the SUN,
and big VAXes indicates that its strengths lie as much with its adaptability
and portability as with some Procrustean bed of a "style" which it enforces
on applications written for it.

As for the particular application that I have trouble with a 16-bit address
space for, it's a word processor.  NOTE that Syntrex's word processor, running
on an 8086, requires overlaying, so there's one limitation on the address
space (physical as well as logical) right there.  Furthermore, the spelling
checker code in our word processor is completely integrated with the
editor.  Yes, you could hive it off into another process.  If we kept the
current user interface - which is VERY nice, since you can define a block and
run the spelling checker on that block while editing - the changes needed to
make it multiple processes would be rather kludgy.  We would have to keep a
"speller" process around in the background (the overhead for a fork and exec
would be too much if the user only wanted to check one word), and we would have
to construct a complex protocol to pass information between the speller and
the editor.  The alternative is to separate the editor and the speller.  This
would be wonderful - penalize the user because of the address space limitations
of the machine!  Sorry, a user interface involving an editor and a speller
which were two separate programs would be LOUSY.  There is NO argument to the
contrary.  (And I'm not the only person to say that; several reports, such as
those in "The Seybold Report on Office Systems", repeatedly complain about
systems where you do have to switch between the editor and the spelling checker.
The company from whom we bought the spelling checker also indicate that one
of the biggest complaints they receive is that it is hard to integrate the
editor and the checker.)

If you don't take careful aim before blasting away, you may end up shooting
yourself in the foot...

					Guy Harris
					RLG Corporation
					{seismo,mcnc,we13}!rlgvax!guy