On Fri, 20 Sep 2002, Dan Veeneman wrote:
  As a follow-up to the DG Nova 3/12 rescue, I've
taken a bunch
 of photos of the system and added what commentary I could.
 You can see the whole thing at
 
http://www.decodesystems.com/dg-nova3/ 
The Analog Devices MPX8A is a multiplexer of some sort. I think the
databook you need is the Analog Devices Module Subsystems Volume 1. I have
Volume 2, but it does not cover that device.
-Toth