PDP-11/23 up and running RT-11

From: Ethan Dicks <dickset_at_amanda.spole.gov>
Date: Mon May 24 20:15:19 2004

On Mon, May 24, 2004 at 08:33:39PM -0400, David Betz wrote:
> I solved my boot problems and now have my new PDP-11/23 booting RT-11!
> Now I just have to sift through the boxes of floppies to see what
> software I have. Apparently the -12 supply isn't necessary to boot the
> system.

Hmm... maybe you should check your comm ports... I know that's one thing
that's inconsistent in the DEC world - reliance on -12V from the bus.

The first rev of Qbus COMBOARD pulled -12V from the bus for the 1488/1489
EIA level shifters. We shipped a board to an early adopter and it failed.
Apparently, that particular chassis did _not_ provide -12V (I don't recall
what the customer had, but we would have tested our design in a BA-11M
and a BA-23).

Rev 2 has a +5/-12V converter in the lower corner. I still have a gross
of them from unbuilt stock. Many modern designs have moved to MAX232-like
drivers; we might have, too, except we were supporting two fully-handshaked
sync serial ports - that's a lot of MAX232 chips and (at the time) expensive
tantalum caps. I think our cost on the voltage converters was on the order
of $12-$17 each, which was marginally less expensive than changing driver
chips, but the engineering to retrofit it to an existing design was trivial.

We also drove 50' cables routinely... not sure how well a MAX232 works over
longer wires.


Ethan Dicks, A-130-S      Current South Pole Weather at 25-May-2004 01:00 Z
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Ethan.Dicks_at_amanda.spole.gov     http://penguincentral.com/penguincentral.html
Received on Mon May 24 2004 - 20:15:19 BST

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