PDP-11/40 modified to be a PDP-11/23

[Glen Slick]

On Wed, Jun 22, 2016 at 5:28 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
>
> I looked at the backplane pictures that I took after the rescue. I assumed
> that the hex-wide 8-slot backplane in the front of the card cage was the
> original 11/40 processor backplane. On the back it says "LSI 11 BACKPLANE",
> so the operation is not so mysterious. I had never seen a hex-wide Q-bus
> backplane before this.
>
> There are some pictures of the system and the Q-Bus to 11/40 front panel
> interface here: http://www.ricomputermuseum.org/Home/equipment/dec-pdp-1140
>

Maybe a DDV11-B? See pages 205-210 of the PDP-11 Microcomputer
Interfaces Handbook 1983-84:

http://www.bitsavers.org/pdf/dec/qbus/EB-23144-18_QbusIntrfs_1983.pdf

The screws on the connector blocks in groups of 1 on the first and
last rows and 3 in the center rows looks similar to those shown in
Figure 2 DDV11-B Module Installation and Slot Assignments on page 207.