Building a PDP-11 for the first time - test-drb@ccmp.vtda.org

14 Dec 2003

On Dec 14, 17:47, Jerome H. Fine wrote:
...
  Pete Turnbull
wrote: 
 > No, not true.  There are both dual and quad 11/73 (the quad being an
...
  > 11/73-plus).  The 11/73 was 15MHz, the 11/83 was
always sold as 18MHz.
...

 Jerome Fine replies:

 While I have heard of a PDP-11/23 PLUS, I don't think
 that "PLUS" was ever applied to the PDP-11/73 boards. 
I doubt it was an official designation, it's just what we (CFM) called
them if they were in BA11-N boxes.  The microPDP-11/73 machines in BA23
boxes always used the quad board, or course, so we never needed to
distinguish.

...
  From what I
understand, for the PDP-11/23 boards, the  "PLUS" could mean either the
ability to address all 4 MBytes
 of memory with the dual M8186 boards (I understand that
 the original M8186 boards were able to address only 256
 KBytes) or that the quad M8189 board was being used. 
"plus" specifically meant the quad board, with the on-board boot ROMs,
LTC and SLUs.  All but the very first of revision of the dual boards
can also address 4MB.

...
  As for the PDP-11/73 boards, I had heard that some
 did have the 18 Mhz crystal, but that might also have
 been done privately.  Megan Gentry just mentioned
 that she changed the crystal on her PDP-11/83 board
 to 20 MHz and it ran correctly. 
As far as I know, all the ones sold as 11/83 were 18MHz, all the ones
sold as 11/73 were 15MHz.

...
   So does the
11/73, though it's different. 
 This answer was with respect to the boot ROMs.  I have
 both a KDJ11-BB (M8190-AB) and a KDJ11-BF
 (M8190-AE).  Aside from the 15 MHz vs the 18 MHz
 crystal, the fact that the latter also had the FPU chip
 was standard with the KDJ11-BF.  But the rev number
 of the J11 chip on the KDJ11-AB is 04 and the EPROMs
 are version 395E5 / 396E5 which can also be the EPROMs
 for the KDJ11-BF.  However, I understand that the J11
 rev number when an 18 MHz crystal is being used must
 be at least 08 and maybe 09. 
Then I'm sure that your ROMs must have been changed at some point in
the past.  The 11/73 never had the same boot ROMs as an 11/83 unless it
was upgraded (which was quite common).

...
  So the dialogue for the PDP-11/73 and the PDP-11/83
can
 be identical - it just depends on which version of the
 EPROMs is being used. 
Of course.  The dialogue is in the ROMs, after all, and people did
upgrade them (to get the ability to boot newer devices, for example).

...
  All this discussion seems to point out that the
PDP-11/73,
 PDP-11/83 and PDP-11/93 boards were not identical 
I disagree -- I don't see anything to differentiate an 11/73 board from
an 11/83 from an 11/84, except the clock and the boot ROMs.  Sure,
different revs of J11 were used.  The original spec was for a 20MHz or
25MHz chip but it didn't meet the spec.  Sure, there were FCOs and
ECOs, but they applied to both 11/73 and 11/83 (and presumably 11/84).
 You've shown yourself exactly what I said, that if you use PMI memory,
the system thinks it's an 11/83 and if you use non-PMI memory, it's an
11/73.

...
  nor did they use the same J11 CPU chip all the time,
although
 the last 09 rev CPU chip that was used with the PDP-11/93
 would probably work with all of the others, just NOT the
 other way around with the early 04 rev CPU chips. 
Agreed.

-- 
Pete						Peter Turnbull
						Network Manager
						University of York