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

[Michael Thompson]

On Tue, Jun 21, 2016 at 9:05 PM, Michael Thompson <
michael.99.thompson at gmail.com> wrote:

> The RICM just picked up a PDP-11/40 chassis that was modified to accept a
> PDP-11/23 board set. It also contains a custom board to interface the
> PDP-11/23 to the original PDP-11/40 front panel. It is quite an
> accomplishment to get the Q-Bus board set working in the Unibus chassis.
>

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

-- 
Michael Thompson