KDJ11-B in a PDP-11/23 backplane?

From: Pete Turnbull <pete_at_dunnington.u-net.com>
Date: Thu Sep 16 18:49:43 2004

On Sep 16 2004, 12:39, David Betz wrote:
> I have a PDP-11/23 with an H9270 backplane and am thinking of
> to a J11 processor. I would like to use the KDJ11-B quad size board
> (M8190-YB). Is that going to require me to use a different backplane?


> If so, is there one that will fit in the same space as the H9270


> and use the same power supply?


The H9270 is a serpentine backplane, with QBus on A+B slots and also on
C+D. The quad KDJ11s use C+D for other things (PMI memory, mainly) so
you can't put them in a serpentine backplane slot; they have to go in
one that has straight QBus on A+B and the CD interconnect on C+D.

The only standard DEC 4 x 4 backplane is that H9270, though some of the
Plessey or other third-party backplanes might be the right size.
  Either you need to modify that backplane to isolate the C and D part
of the first slot (and then jumper the QBus signals to the C and D
parts of the next slot -- one way to achieve this might be to just
remove the connectors), or you need to modify (with a saw!) some other
backplane to fit, or you need a different chassis, or you need a
KDJ11-A (dual height). If you only need 4 slots you might be able to
adapt an H9281-A, which is 2 x 4, to fit.

The PSU should do (providing you don't exceed the current ratings) -- I
assume it's an H780? Is it in an BA11-M chassis? If so, it's
originally been a PDP-11/03, and someone has upgraded it.

The other thing is that the H9270 is only 18-bit (as are the H9281-x
series, unless they have a "Q" in the part number). That in itself
shouldn't stop a 22-bit processor working (your 11/23 is 22-bit) but it
wouldn't be able to use more than 256KB (128K words) of adddress space.
 It would behave as if the top 4 address bits were always 0. You could
upgrade it to 22-bit by jumpering BC1, BD1, BE1, BF1 from each slot to
the next. If you do that, check what you're using for termination --
it's probably only 18-bit as well (if it's a BDV11, there's a fairly
easy FCO for it).

The normal backplanes for a KDJ11-B are H9276 (22-bit, 4 x 8, straight)
which is used in a BA11-S; H9278 (22-bit, 4 x 8, first 3 slots
straight, rest serpentine) which is in a BA23; BA123 backplane (22-bit,
4 x 13, first 4 straight, next 8 serpentine, and the last slot is
power-only) which doesn't have an "H" number. However, BA11-N systems
with an H9273 backplane were sometimes field-upgraded and may or may
not have had the extra four address lines wired.

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Thu Sep 16 2004 - 18:49:43 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:37:29 BST