ToDo PDP-11/70  'in-a-box' DIGITAL


INTRODUCTION
So far I have built a replica of the 11/35 console, and a replica of the pdp8/e console. The 11/35 uses the Blinkenlight Boards to control the lamps and the switches and communicates over a serial link with a PC that runs a patched version SIMH. The pdp8/e goes a step further, the 6809 does not only control the lamps and switches, but it also simulates the pdp8/e itself!
This project started with a few auctions on eBay. In the same time frame a complete front panel was offered for the HP2117F and the HP2113E. I thought it would be nice to show that the Blinkenlight Boards can be put to use in more than just DIGITAL consoles. This is (probably) the last project, because one week later a full 11/70 console appeared on eBay. I had to get this, and in the frenzy I paid perhaps a bit too much for it ($300), but the panel is in perfect shape cosmetically.
On request, I can e-mail the original pictures (3 to 4 times as big) with lots more of construction details.


CONSTRUCTION
This project will be a complete PDP-11/70 'in-a-box', which means that it has the real console.
Inside the box are the following components, that will make it a stand-alone PDP-11/70 simulation.

11/70 console box

Bottom and chassis
I made the bottom plate of 5 mm thick aluminum for two reasons. First it gives the box some weight, because you want to push down the switches without the box tilting, and second you can use screws that go completely in the plate which will prevent making scratches on the table.
Also, the bottom plate is a few inches shorter than the front panel. I used "L-shape" aluminum profiles on the bottom plate to install the side panels. In this way, you get at the bottom sides left and right a small edge to pick up the box. The back plate of the 11/70 console has already four threaded holes that can be used to mount the panel on the bottom plate. I mounted the front panel at approximately 80 with two brackets to give the panel a nice view angle and "ergonomic" access to the switches. If you do not have the tool to bend the aluminum, you can use standard L-shaped ALU profiles; you just need to drill a few more holes ...
Here are a few detail pictures to give you an idea how I built the box.

bracket and edge panel, bracket and L-profile panel corner
mounting bracket and "L-profile"11/70 panel, bracket and "L-profile"panel corner with bottom plate

The bracket has two 90 edges. The slanted edge is mounted against the rear of the front panel, the straight edge is mounted onto the bottom plate (with the L-profile edge in between). To fit the L-profile, the end at the panel side must be cut a little. On the picture at the right you can see how the bottom plate hides behind the rim of the front panel, and how the L-profile and the bracket are mounted. Between the L-profile outer side and the vertical rim of the front panel is 2 mm space: exactly the room to install the side plates.
Practical tip: keep the "L-profile" strips a bit too long. When you put all together, you can cut off the excess of length.

Bottom and chassis
Just like the bottom plate, the side panels move behind the sides of the 11/70 console frame. I first cut the shape of the panels out of cardboard, before I made them in aluminum. Then I drilled the mounting holes and made the L-shaped edges to mount the panels.

As I figured that it would be handy to have a 3" floppy disk drive installed (for the built-in PC), I made an opening in the panel at the right side, and cut a rectangle out of the bracket that holds the 11/70 console. Using 3 pieces of L-shaped aluminum I mounted the floppy drive on this bracket. A small bracket fixes the outer right side panel with the bracket to make the whole construction more sturdy, as you will be pushing the floppy disk eject button!

rear - left side rear - right side

Mounting plate for the electronic stuff
As I did not want to dismantle everything every time I will add a part as this project progresses, I decided to build all the electronics on a mounting plate. On this mounting plate I will install the single-board PC, the Core and the I/O Board, and the hard disk for the PC.
The mounting plate is a simple rectangular piece of aluminum which I bent 90 at one long side to make the plate sturdy. The mounting plate is installed with two L-profiles to the brackets that hold the 11/70 console. As I had a few rubber dampers (piece of rubber with separate screws at both ends, I installed the mounting plate through these dampers on the L-profiles. This construction absorbs shocks to prevent damage to the hard disk, and quiets the sound of the hard disk. As you can see, the electronics is installed on the mounting plate, and the hard disk is installed under the mounting plate using (again) 2 pieces of L-profile.

Power supply installation
The modern PC power supplies do not have many holes to install it in a hobby enclosure, and require that some sides do not block the flow of (cool) air. To mount the supply I decided to split the rear panel into two pieces. The bottom piece is made of a strip of steel that has many small openings.

PC installation and connections
When the hard disk, the floppy disk drive and the power supply are installed, it is time to install the single-board PC.
Make all the necessary connections, for now that are the following.

As this depends much on the single-board PC you use, you will know better than me what to do.
Perhaps you choose for no installation of an internal PC, but use an external PC ...
When everything is tested you can add the connection of the second serial COM port, the parallel port and all other interfaces that the PC board supports (like a network connection) to connectors at the rear side of the "stand-alone PDP-11/70".

rear side with PC connections

Blinkenlight Boards installation
To fit all on the mounting plate, I installed the Core Board and the I/O Board stacked to each other.
The Core Board is first installed on the mounting plate. Connect the serial port of the Core Board straight to the COM port of the internal PC, or to a 25-pin (or 9-pin) D-SUB connector at the rear side when you use an external PC. Connect the +5V. and Gnd pins of the Core Board to the PC power supply. Connect the (Core) reset button (optional, but might be useful). Plug the flat cable on the Core-I/O header.

Install the I/O Board. Connect the +5V. and Gnd pins of the Core Board to the PC power supply. Connect the other end of the flat cable from the Core-I/O header on the Core Board to the Core-I/O header on the I/O Board. Make sure pin #1 aligns.
This wiring is not complex.

I/O Board to PDP-11/70 console connection
This is where most of the electrical work is ...
All LEDs, switches etc. on the PDP-11/70 console are connected to three 40-pin ribbon cables with IDC headers. The input ports and output ports on the I/O board are grouped per 2 ports on a 16-pin header. So, I needed some sort of "interconnection" board to make the transistion from the I/O headers to the headers on the PDP-11/70 console board.

First, I defined the allocation of the input ports and output ports to the LEDs, switches etc. in the Core Board firmware.
I have done that and made a new firmware EPROM, which also contains a few more interface functions that can be called to control the LEDs in an efficient way (read: less message bytes from SIMH to the Core Board, thus improving performance).
The following table shows the allocation.

The OUTports connect to the LEDs via the drivers on the PDP-11/70 console board.
I/O portbit 7bit 6bit 5bit 4bit 3bit 2bit 1bit 0
OUT8D15D14D13D12 D11D10D9D8
OUT7D7D6D5D4 D3D2D1D0
OUT6A15A14A13A12 A11A10A9A8
OUT5A7A6A5A4 A3A2A1A0
OUT4- -- -A21A20 A19A18A17A16
OUT3RUNMASTERPAUSEADRS ERR PAR ERRIND DATAMMR0 [1]MMR0 [0]
OUT2- -- -- -PAR HI PAR LO22BIT18BIT16BIT
OUT1- -- -- -- - - -- -- -- -
 
The INports connect to the toggles, switches and rotary switch contacts of the PDP-11/70 console board.
I/O portbit 7bit 6bit 5bit 4bit 3bit 2bit 1bit 0
IN8- -- -- -- - - -- -- -- -
IN7- -- -- -- - - -- -- -- -
IN6- -- -- -- - - -- -- -- -
IN5PANL LOCKHALTS/BUS CYCDSP DATA [1] DSP DATA [0]DSP ADRS [2]DSP ADRS [1]DSP ADRS [0]
IN4DEP- -- -- - CONTLOAD ADRSSTARTEXAM
IN3- -- -SW21SW20 SW19SW18SW17SW16
IN2SW15SW14SW13SW12 SW11SW10SW9SW8
IN1SW7SW6SW5SW4 SW3SW2SW1SW0

When all connections are defined you know on which pin of which INport or OUTport header a switch or LED must be connected.
The PDP-11/70 console panel has four connectors, and you need them all four. One is the 8-pin Molex connector for the power supply of the LEDs and (most of) the logic on the console board, the other three are BERG connectors through which all switches and LEDs are connected to the I/O Board.
(Right-)click the following link to get a copy of the  PDF file description of the 11/70 console board  (5 pages, 507 kb)  from the bitsaver's mirror site. I will refer to these pages a bit further down this page.
You see the three 40-pin connectors, named J1, J2, and J3. The pins on these connector are named as follows.

DEC connector pin naming
connector viewed at female plug entry side

PDP-11/70  connector  J1
pinassignedpinassigned
A PAR HIB PAR LO
C - -D - -
E - -F - -
H - -J - -
K - -L - -
M - -N - -
P - -R - -
S - -T - -
U - -V - -
W - -X D0
Y D1Z D2
AA D3BB D4
CC D5DD D6
EE D7FF D8
HH D9JJ D10
KK D11LL D12
MM D13NN D14
PP D15RR GND A
SS DSP DATA [0]TT DSP DATA [1]
UU - -VV GND A
PDP-11/70  connector  J2
pinassignedpinassigned
A ADRS ERRB PAR ERR
C A9D MASTER
E A8F PAUSE
H A7J RUN
K A11L A17
M A10N A16
P A6R A12
S A3T A13
U A2V A14
W A1X A15
Y A5Z A18
AA GND BBB A19
CC A4DD A20
EE A0FF A21
HH DSP ADRS [0]JJ MMR0 [1]
KK DSP ADRS [2]LL PANL LOCK
MM DSP ADRS [1]NN MMR0 [0]
PP +5VBRR - -
SS IND DATATT - -
UU - -VV GND B
PDP-11/70  connector  J3
pinassignedpinassigned
A SW0B SW1
C SW2D SW3
E SW4F SW5
H SW6J SW7
K SW8L SW9
M SW10N SW11
P SW12R SW13
S SW14T SW15
U SW16V SW17
W SW18X SW19
Y SW20Z SW21
AA GND CBB CONT
CC - -DD S/BUS CYC
EE - -FF LOAD ADRS
HH - -JJ START
KK - -LL EXAM
MM - -NN DEP
PP HALTRR +5VC
SS 16BITTT 18BIT
UU 22BITVV GND C

How (which order/sequence) you connect the connector pins to the I/O Board is not particular important as you assign the output port bits in the software. However, it is clever to allocate the Address and Data Switches and LEDs in the proper sequence, that is bit 0 = D0, bit 1 = D1, etc. If you connect everything as I show on this page, you can ask me for the modified firmware.
The text in orange boxes are outputs (LEDs), the text in green boxes are inputs (switches/toggles) for the I/O Board, text in white boxes is power supply, and the text in grey boxes is not connected or not used.
The picture shows how I built the interconnection board. The blue 6-screw connector is wired to the 8-pin Molex connector J4 of the console, and the 4-screw connector is the connection to the PC power supply (+5 Volt, Gnd, and the two connection to activate the ATX power supply via the console key switch!)   The 4-pins marked "+" and "-" are the power supply connections to the Core and I/O Board.

component side interconnection board
solder side interconnection board

 
interconnection board lay-out
If you want to "stack" the Core and I/O Board together with the interconnection board, you could build the interconnection board the following way (just a suggestion).
Given the assignments of the I/O on the 16-pin headers on the I/O Board and the signals on the connectors J1, J2 and J3 of the PDP-11/70 console board, I suggest the following lay-out for the interconnection board.

If the interconnection board dimensions are 100 x 160 mm ("Euro card" size), you can mount the I/O Board on top of the interconnection board with hexagonal stand-offs. The "holes" in the figure indicate where the I/O Board will be mounted. The Core Board can be mounted on top of the I/O Board using hexagonal stand-offs. Of course, this depends on how you want to make your construction. I promised Edward to assemble a Core and I/O Board, and build an interconnection board for his PDP-11/70 console, and I will do his board this way.

If your PDP-11/70 console has the black metal plate at the rear side (used to mount the console on the front of the processor box), you can also mount the 3 boards (Core, I/O and interconnection) next to each other on the metal plate. Doing so, all electronics upto the RS-232 connection can be built with the PDP-11/70 console having minimal depth. However, you need some depth for the housing to make it standing well on a table while pushing the switches ...

There is no need for male headers with a shroud, but if you use headers with a shroud check the "opening" at one long side of it. That is the side where the odd-numbered pins are. As you can see from the pictures I did that not entirely correct. It is not really an issue, as long as you make sure that pin #1 at one end of the ribbon cable matches on the boards with pin #1 at the other end (or solder the interconnection board wiring between the 16-pin headers and 40-pin header in such a way that the end-result is correct).
Just solder a few wires on the interconnection board, and then check!   This is how I did it.
First I soldered all 16-pin and 40-pin headers on the board, then I only soldered the wires for "PAR HI" and "PAR LO" from J1 to OUT1-2. I applied +5V to the PDP-11/70 front panel board (via the 8-pin Molex connector). As all LED driver inputs are floating (not connected) all LEDs will be lit, except the LEDs that indicate the setting of the 2 rotary switches. Then I plugged connector J1 from the PDP-11/70 board in the header on the connection board. When pin #9 of the OUT1-2 header is connected to GND, the LED "PAR HI" should go off. Likewise, when pin #16 of the OUT1-2 header is connected to GND, the LED "PAR LO" should go off.
When you checked this, you know you got the location of pin "A" and pin "B" on connector J1 correct. Now it is easy to solder the wires for all DATA LEDs from J1 to OUT7-8. The way you do that is a matter of choice, but I soldered one entire row (D0, D2, D4, D6 ) before I soldered the other row (D1, D3, D5 ...). This way you can better keep track of what you are doing; I make less errors with this way of soldering lots of pins ...
The same goes for the pins of connector J2. Only connect "ADRS ERR" and "PAR ERR". Check that the correct LED goes off when you ground the correct pin on the 16-pin header, then solder the other ADDRESS and some of the status LEDs.

More to follow ...