[TUHS] pdp11 question

Pete Turnbull pete at dunnington.plus.com
Thu Nov 18 09:36:38 AEST 2010

Wilko Bulte wrote:
> 11/73:
> http://www.chookfest.net/computers/pdp1173.html

Unfortunately a few things on that page are inaccurate.  For example, 
it's not exactly a PDP-11/83, it's really a microPDP-11/73, although the 
memory has been rearranged as the writer stated.  Both microPDP-11/73 
and /83 use KDJ11-B, the difference being that the /73 used 15MHz parts 
(as in that one) and the /83s which came later had 18MHz parts, and more 
importantly they have different boot ROMs.  However the other and 
arguably most important difference between /73 and /83 systems is that 
the /73s were originally set up with a normal QBus memory configuration, 
whereas /83s use PMI memory with the memory in front of the CPU instead 
of behind it.  The boards in this one have been re-ordered, and although 
having the CPU for a microPDP-11/73 it will mostly behave as a 
slightly-slow /83.

KDJ11-A boards were used as upgrades for rack-based 11/23s and OEM 
systems, not microPDP-11s.  So the one on that page is close to its 
original configuration, except for the Dilog SCSI controller and the 
memory arrangement.

Pete						Peter Turnbull
						Network Manager
						University of York

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