On Nov 29, 2016 11:44 AM, "Peter Coghlan" <cctalk at beyondthepale.ie>
wrote:
 Another thing I noticed is that there are rather more than 50 QBUS signals
 listed on the top right of the circuit diagram.  I guess which ones are 
omitted
  from the 50 pin D connectors will become apparant when
I find a pinout for
 those connectors.  I suppose the power rails and those labeled "spare" are
 likely candidates for omission.
 
There are *two* 50-pin bus extension cables, not just one. More than enough
signal lines for the 72 card edge fingers on a dual wide card. (18 per 2
sides per the A and B card edge connector positions).