RSTS/E and PDP 11/23

From: Ethan Dicks <>
Date: Mon May 17 17:58:59 2004

On Mon, May 17, 2004 at 06:39:18PM -0400, David V. Corbin wrote:
> If memory serves me, there was a significant interval where the 11/23 BOARD
> had 22-bit addressing, but the standard backplane/chassis only had 18 bits
> wired. Been about twenty years, and I am doing this from memory.

Right... the BA11N is one of the Qbus boxes I have the most experience
with... it comes from the factory as 18-bit, but can easily be upgraded
to 22-bit. You have to use a 22-bit bus terminator or upgrade your
18-bit terminator, but it works. OTOH, ISTR there's an old LSI-11
CPU that used the "unused" bus lines for memory refresh, so that would
be out of the question after the upgrade.

These days, though, unless you are striving for some sort of visual
authenticity, it's just as easy to throw your boards into a BA23
chassis and go from there. I have more BA23 boxes than I have uVAX
CPUs, so it's an easy choice. But if all you have is an 11/23 in
a BA11 of some flavor, you _can_ max it out.


Ethan Dicks, A-130-S      Current South Pole Weather at 17-May-2004 22:50 Z
South Pole Station
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Received on Mon May 17 2004 - 17:58:59 BST

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