DEC PDP-11/73 in BA123 cabinet

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I have built up a PDP-11/73 system in a BA123 cabinet.

My aim is for this system to be able to boot either RT-11 V5.7 or RSX-11M+.

The primary MSCP controller is a CMD CQD-220 controller with a SCSI2SD device connected to it. Up to 4 logical devices can exist on the one SD card.

The secondary MSCP controller is an RQDX3 connected to the BA123’s M9058 breakout board. Connected to that is an RD31 (Seagate ST225) and two RX33 5.25″ floppy drives (Teac drives).

Backplane Configuration

The table below shows how the backplane is currently populated.

M8190-AB (KDJ11-BB)
Camintonn non-PMI RAM board
Camintonn CMLV11-J (4-port SLU) Empty
M8029 (RXV21) Empty
M8061 (RLV12)
M3104 (DHV11-A)
M3104 (DHV11-A)
CMD CQD-220 (SCSI) M7516 (DELQA)
M9047 (Grant Continuity) M7555 (RQDX3)

There is an excellent table comparing the various DCJ11-based processor board here.

SCSI2SD configuration

I plan to use a SCSI2SD board as the primary hard drive for the BA123. This will make it easy to transfer PDP-11 hard drives between the BA123 cabinet and SIMH (all I will need to do is copy the relevant SIMH virtual file to/from the relevant sector range on the MicroSD card, using the Linux “dd” command).

Details of the SCSI2SD setup are here ->

Doing a SYSGEN in RT-11 V5.7

I found this helpful dialog showing the typical SYSGEN Q&A process:

The RT–11 System Generation Guide (for RT-11 Version 5.6) Order Number AA-M240E-TC is also very helpful reading.

The main changes that I made during the RT-11 V5.7 SYSGEN were:

  • Provide for 4 x DLV11-J ports (of these one will be the system console, one will be for a TU58 emulator, and a third port will be for a serial printer)
  • Provide for 3 x MSCP controllers
  • Provide for at least one 8-channel multiplexer
  • Add a “DD” device driver (for TU58 support)

I did the sysgen on real hardware (a PDP-11/23, with two MSCP devices installed). Once that was done, I read the system disk (which was on an SD card) back into a Linux computer, using the “dd” command. The resultant file is “rtv57-sysgend.dsk” and is inside the ZIP file called “”. Note to self: The primary source of this file is in the /Downloads/images directory on the N40L Microserver. A second copy is in the same directory on the Raspberry Pi named “rpi-sd”.

The print out below shows how the DU devices have been assigned in this image:


Device    Status                   CSR     Vector(s)
------    ------                   ---     ---------
  DU      Resident                172150   154 150 144

          DU0: is set PORT =  0, UNIT =  0, PART =  0
          DU1: is set PORT =  0, UNIT =  1, PART =  0
          DU2: is set PORT =  0, UNIT =  2, PART =  0
          DU3: is set PORT =  0, UNIT =  3, PART =  0
          DU4: is set PORT =  1, UNIT =  0, PART =  0
          DU5: is set PORT =  1, UNIT =  1, PART =  0
          DU6: is set PORT = *2, UNIT =  0, PART =  0
          DU7: is set PORT = *2, UNIT =  1, PART =  0
          D10: is set PORT =  0, UNIT =  4, PART =  0
          D11: is set PORT =  0, UNIT =  5, PART =  0
          D12: is set PORT =  1, UNIT =  2, PART =  0
          D13: is set PORT =  1, UNIT =  3, PART =  0
          D14: is set PORT =  1, UNIT =  4, PART =  0
          D15: is set PORT = *2, UNIT =  2, PART =  0
          D16: is set PORT = *2, UNIT =  3, PART =  0
          D17: is set PORT = *2, UNIT =  4, PART =  0
          * Port unavailable


Moving the SYSGEN’d RT-11 V5.7 to the BA123 cabinet

When I moved the dual-MSCP setup to the BA123, I had a problem booting up RT-11 V5.7. Each time (and no matter whether I was booting from the SCSI2SD drive DU0 on the first MSCP controller, or from the RX33 on the second MSCP controller), the boot process would start but then give the following error: “mon-f-trap to 4 012703”. This was caused by me not having a DLV11-J in the BA123 cabinet (I had selected a DLV11-J during the SYSGEN process). Once I installed the DLV11-J (with Console on Channel 4 disabled), the SYSGEN’d RT-11 V5.7 would now boot successfully from either the SCSI2SD board or from the RX33 floppy drive.

DLV11-J Bulkhead

To Physically connect the DLV11-J to the outside world I used a bulkhead that DEC calls a “DLV11-J Filter Panel”. This bulkhead has 4 x DB25M connectors on it, which can be used to connect up all 4 ports on a DLV11-J. The DEC Part Number is 5415221 (the “21” is however hidden beneath the 40-pin Berg header), and the PCB is marked “5015220”. The schematic for this panel are available here -> CKDLVJ1 Field Maintenance Print Set, DEC Part Number MP00990-01. Page 13 of the MP00990 Field Maintenance Print Set shows how DEC connects between the DLV11-J and a DB25M plug.

Not also that there are other similar-looking panels that are NOT compatible with the DLV11-J, so check the part number or PCB number before using it. For example there is a H3173A (with PCB number 50-15599-01), which appears to be designed for use with DHV11 (terminal multiplexer).

RSX-11M-Plus Manuals and Information

Here are some links to some useful documentation: