More 11/44 basic newbie help request

From: Jeffrey S. Worley <Technoid_at_30below.com>
Date: Tue Feb 11 10:21:00 2003

I thought it was silly too when I first laid eyes on such a system, but
after some experience with it, I understand why. There may be other
reasons as well, but here's my take on it.

No one knew just what they or other folks were going to hang in these
backplanes, or what functions those cards would perform. If they had
known, it would have been pretty simple to provide a set of jumpers or
some other (easier) means of moving signals around, but they didn't so
they went for total flexibility in this department and so required
jumper wiring.

Some card slots don't carry certain signals over to the next slot down
the line if there is no card installed in that slot.

For example. If you have an hdd controller in slot A, a blank slot B,
and a serial terminal controller in slot C, my machine wouldn't work at
all. In this scenario, I would have to bridge the blank slot B by
jumping two signals (IRQ and XSTL?) from A to C in order for those two
critical signals to propagate past the blank slot.

You might wonder why they would omit two of the most important lines
from the backplane like that. Well, it is flexibility in mind here.
With this method, you could have card's B and C connected via ribbon
cable at their leading edges to carry the signal from B to C for use and
then have card C propagate the signals over the backplane after they've
served their purpose. You could even bring those signals outside the
machine entirely to some specialized equipment before returning them to
the backplane via a card. In this way, you could largely replace the
backplane with your own custom wire job.

Regards,

Jeff

-----Original Message-----
From: cctalk-admin_at_classiccmp.org [mailto:cctalk-admin_at_classiccmp.org]
On Behalf Of Jay West
Sent: Tuesday, February 11, 2003 10:04 AM
To: cctech_at_classiccmp.org
Subject: More 11/44 basic newbie help request

Eric wrote...
> Get the manuals from Al's site.

You know... I think I've just been told "RTFM" *grin*
S'ok, was well deserved :)

After perusing the manuals for the 11/44 and the RL02's, and the RL11
(looking for docs on the 8 port mux now).... Most of my questions are
answered there (big suprise). Not trying to start any holy wars or
anything,
but to my "newbie with unibus" mind, the design of having to change
backplane wiring for certain cards seems to be rather... ummmm silly
(euphamism{tm}), at least as compared to other systems of the period.
Probably there is something I'm missing as to why this is a good thing.


Jay West
Received on Tue Feb 11 2003 - 10:21:00 GMT