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Path: tekfdi!mhorne
From: mhorne@tekfdi.TEK.COM (Mike Horne)
Newsgroups: mod.computers.68k
Subject: Rehash: MMUs and the fate of computers to come
Message-ID: <795@tekfdi.TEK.COM>
Date: 24 Feb 87 22:16:50 GMT
Reply-To: mhorne@tekfdi.fdi.tek.com
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 72

In an earlier article, mwm writes...

> Gee, the biggest, fastest Unix box I can get to (both legitimately and
> otherwise) doesn't have VM. Their attitude is "Real memory for real
> performance."  Maybe the hardware designers know something you don't?
> If not, "how come you ain't rich?" :-)

Make that "Real memory for real bucks."  Also note that hardware designers
work on projects that last 2 or 3 years.  Give Atari, Apple, Commodore, SUN,
Apollo, etc. etc. a call on the phone and ask them if their new machines to
be released in the next year or two are using VM.  If they aren't, check the
business obituaries daily.  But, I think you will find that they are.  Atari
is.  Apple is.  SUN and Apollo have been for years.  And the list goes on...

> There's a place for everything. Given a 68K based system, I'd rather
> not have virtual memory - just give me 16Meg of real, and forget the
> virtual. An MMU would still be nice, though. But if I can save 10% of
> the cost of producing a box, and I'm planning on selling it in a
> market that doesn't need an MMU, then I'd be stupid to put one in.

Think about what you just said.  "Save 10%."  Now, what if we had just put
in 2 MB of DRAM and a swapper with an 16MB swap space.  Now, think about
how much that additional 14 MB of DRAM is going to cost if you have a 16 MB
system.  Try (using 1Mb DRAM chips) 20 bucks per chip times 8 chips times
14 sets.  That's 2240 buckaroos, bud.  Oh, and don't forget the price of
the support chips.  I think I can find a pretty good MMU for that price,
plus maybe a 200 MB hard drive (OEMs can get a 200 MB hard drive for < $1500,
quantity 100 or so) too.  Simple math.  Of course, the price of RAM will
drop.  But so will MMUs and HDs.

So, what does this get me?  Well, it doesn't get me 16 MB of real memory,
but it does get me a nice HD and true multi-tasking capability for the same
price.  In addtion, as far as my programs are concerned, I truly have a
16 MB address space.  What will the customers want for storage?  Floppies
or an HD?  I think we all know the answer to that one. 

> For instance, that's why the Amiga doesn't have an MMU; they looked at
> it, and were looing at $125 for the CPU board. Even at $10 for the

Again, the Amiga is 'old' in comparison to todays technology available to
the designer.  True, when they designed it, an MMU may have been expensive,
but companies don't turn out new computers every couple of months!  It is
a very long and difficult process (try years).  Nevertheless, todays design
engineers can take advantage of much cheaper and much more powerful chips
than when the amiga (or ST, or Mac) was designed.  And they are.

> As for Unix proper - it's got serious problems. The worst is that the
> system calls have long since gotten past the point of having been
> designed, and have "grown" to be what they are. Starting over from
> scratch, and building a system that emulates Unix on top of a
> reasonable OS (which is what Minix is) is a _good_ thing. Period. The
> trick is to then get all those Unix utilities (hopefully, after
> rewriting them to regularize the argument parsing & delete cruft
> that's been added to solve problems you solved in a better way)
> running on your system. That's harder, 'cause you have to talk AT&T
> out of the sources, or rewrite all of them.

I tend to agree that UNIX is not as easy to learn as some other OSs.
Yet, it is very powerful.  One cannot overlook the power of an OS/language
just because it may be difficult for some people to learn.  It's the
same old "Why should I learn it if I can't understand it in 5 minutes"
attitude that raises all of these "I hate XXXX OS/language/computer"
comments.  Still, I agree that there is room for improvement.  There always
is.

Mike

------------------------------------------------------------------------
 Michael Horne - KA7AXD              FDI group, Tektronix, Incorporated
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