"Real Computers" (was Re: Trivia Question)

From: Patrick Finnegan <pat_at_purdueriots.com>
Date: Fri Feb 21 22:11:01 2003

On Fri, 21 Feb 2003, Eric Smith wrote:

> I wrote:
> > That's quite a sad definition of "real computer". Any one of my PDP-8
> > or PDP-11 systems, even the wimpiest, is much more of a "real
> > computer" than any PC compatible will ever be.
> Phil wrote:
> > What, even if said PC is a K6-II/400 running Linux?
> Even if it's the dual Athlon XP 1900 running Red Hat 8 which I use
> for most of my software development. There's no question that it
> has orders of magnitude more computing power, memory, and disk, but
> that's not part of my criteria for "real computer":

OK, I've got a few problems with this. Personally, I think you're
confusing the terms 'vintage' or 'classic' and 'real' mostly. For
reference, I'll use three computers. One very new - an IBM p690 "Regatta"
system, a 'just classic' machine ~10-11 y.o.- an IBM RS/6000 model 520,
and a fairly classic machine - an IBM System/36. I've used both the p690
and the 520, and sort-of-used a System/36. Yes, I have 'carefully
chosen' these models to prove a point. If you're not familiar with the
p690, it's basically what would happen if you took an IBM S/390 (their
'current' mainframe arch... well sort of) mainframe and turned it into an
RS/6000. While it doesn't have hot swap CPU or memory, it is about
1/10th the price - the one that Purdue recieved had a street value of
about $1.3M.

BTW I've got a S/36 I'm trying to get up and running, if anyone cares to
help. I've got 0 documentation on the thing. I'll try posting another
message to the list sometime soon about it.

> 1) Is it well-engineered from the ground up?
> PCs: no, a lot of the stuff in even the best PCs is of very poor

OK, I agree with this first point. All three of my examples of 'real
computers' were "well-engineered from the ground up".

> 2) Can it be expected to have a long operating life?
> PDP-8: I've got one that is 27 years old and still works great,

OK, I agree with two points, but realistically, I'd argue point 1 implies
point 2. If it's well engineered, it _should_ have a long operating life.

> 3) Is it documented?
> PDP-8: very well
> PC: barely at all. Just try to get information about what your

OK, here's the first problem I see. 'Newer' IBM systems - well maybe all
three of my examples - are poorly documented down to the component level.
It's actually probably easier to get documentation about the p690 than the
other two examples of mine, but I know you can't get anything as good as
what you'd need to build replacement firmware or parts from scratch.

> 4) Can it be repaired if it breaks?
> PDP-8: definitely.
> PC: no, you throw away a subsystem and get a replacement. The
> problem here is that any given subsystem (e.g., a video card) is
> only on the market for maybe two years; after that you can't get
> an identical replacement. Original-spec PDP-8 replacement parts
> were available for over 20 years.

While not quite the same as 20 years, you *can* still get identical,
new, many year old 'replacement' parts for PCs. It's probably easier to
do that then it is to get new replacement parts for an IBM RS/6000 model
520 or a S/36, in fact. For example, I just bought, as a part of a new
package, a Pinnacle Systems DC10+ video capture card. I *know* that it's
been available for at least 4 years, probably longer than that. There are
some people that maintain products for very long lifespans, such as
lab-equipment interface cards.

One thing I'm slightly suprised about is that you're not claiming that
it's easy to service 'real computers' at the component level. Of course,
that also would be nearly impossible with my examples ;-). That is,
unless, you could get schematics on the systems, and/or owned a chip-fab
facility for all of the custom IBM silicon in these things.

Purdue Universtiy ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
Received on Fri Feb 21 2003 - 22:11:01 GMT

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