[HECnet] pdp-11/83-84

[Dave McGuire]

On 07/05/2012 05:48 PM, Boyanich, Alastair wrote:
Thanks, Yeah   I was more than a bit hot for it also. Looks like it came
out of Ford Aerospace and Comms Corp (P.S. FAAC Best acronym next to our
old one of FACOM which was changed when someone heard a .jp accent
saying "FAKKUM" to one of the clients *G*). No clue how it ended up in
Adelaide unless they were doing defence contracting.

  Yeah really!   But, a great score either way.

  You CAN, however, get a CIS option (if you can find it!) for your
11/23!   I too would love to mess with CIS a bit; I've never done so.
I
have two CIS option board sets for my 11/44s but have not yet
installed
them.

Nice! (tm) .. got a photo's of the 11/44 option?

  Not yet, but keep after me about it and I will photograph the boards.

Really wondering about
the /23Plus. If the option for it is just PROM's that should be pretty
easy to reproduce.

  It won't be at all easy to reproduce.   They are MICROMs.   The F11 CIS
option is one of those multi-chip carriers, but for CIS it is two
40-pin-DIPs wide, and contains six MICROM chips.   These are bipolar
mask-programmed ROMs with an (I think?) undocumented interface.   I would
be more than a little surprised if anyway, even someone of technical
means, could reproduce that.

  Since you have an 11/23+, you are in luck; that has one more 40-pin
socket than the dual-width 11/23 CPU board.   It can accommodate both the
CIS MICROM option and the floating point MICROM option.   On the
dual-width 11/23 boards, you have to remove the floating point MICROM.

  You could remove the MMU chip to make room for the double-wide CIS
chip carrier, but that'd be pointless because, if memory serves, the
floating point registers reside within the MMU chip.

  The 11/24 has yet one more socket, so it has no such limitations.

                      -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA