This page does not describe a PDP-11, but I received this configuration from Kender Thijssen, a company that would otherwise have scrapped this machine. As my collection is focussed on PDP-11's, I justify this addition to my collection as the machine that formed the bridge between the PDP-11 and the VAX time line. The first VAX was the VAX-11/780 which is a big machine. The VAX-11/780 had two decendants, the VAX-11/750 and the VAX-11/730. These two are smaller but are also slower than its big brother.
VAX is an abbreviation for Virtual Address eXtension, and the VAX-11/780 is the basis for all performance comparions between the many VAXen that would be built. The performance figure of the VAX-11/780 is called "one VUP" (VAX Unit of Performance). With this definition, the VAX-11/750 is 0.8 VUP, and the VAX-11/730 is 0.6 VUP (the slowest of all VAXen).
The nice thing about these VAX-11/7x0's is that they show their heritage: they can run PDP-11 software in a so-called compatibility mode, and that is a feature only available in these three models. Actually, the internal hardware consists of the "VAX stuff" with a module that interfaces to UNIBUS, so all PDP-11 peripherals can be connected to these VAXen!   The picture shows from the right to the left, the VAX-11/750, a HSC70, and a cabinet with three RA81 drives, just before I unloaded the cabinets from the truck. I wished I had that much space in the house! And believe me, the cabinet with the three disks is the heaviest (over 200 kilos)! If you click on the picture, a larger picture opens (787x484 pixels, 62 kb).

This VAX-11/750 has served in two locations. It (she?) was used in a Fokker production line. Fokker was a Dutch company that developed and built commercial air planes, but went out of business in 1996. The founder, Anthony Fokker was one of the pioneers in aviation. Later, this VAX-11/750 returned to Kender Thijssen, a company that offered DIGITAL systems (sale/hire) and consultancy and servicing. That company still exists and used the VAX for test purposes. Through the HSC70 they connected disk and tape (RAxx/TAxx) units to run VAX diagnostic programs during a long time for these devices. This VAX operated flawlessly for more than 4 years, so I can be called lucky to own such a reliable system!
I made a gentleman's agreement with Kender Thijssen that I will delete all information on the disks, so as soon as I have some knowledge of (Open)VMS, the Operating System for this machine, I will start up the system to delete everything. I will have to figure out a way to install VMS (I do have a hobbyist license), but that's for later ...

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I received the following documentation from Kender Thijssen with this system.

• Field Maintenance Print Set 11750   (MP00838, Rev. B)
• Field Maintenance Print Set KA750   (MP01024, Rev. A)
• Field Maintenance Print Set FP750   (MP01269, Rev. A)
• Field Maintenance Print Set H7104-C   (MP01020, Rev. A)
• Field Maintenance Print Set L0016   (MP01404, Rev. A)
• Field Maintenance Print Set 875 Controller   (MP01022, Rev. A)

• Field Maintenance Print Set H7104-D 5 Volt Power Supply   (MP01021, Rev. A)
• Field Maintenance Print Set MOS Memory Array M8750   (MP01398, Rev. C)
• Field Maintenance Print Set H7112 Battery Charger   (MP00407, Rev. A)
• Field Maintenance Print Set 11/750 F   (MP01377, Rev. B)

These are the more interesting links I found in my search for information on the VAX-11/7x0 system.
You can find are many links on the Web which deal with running NetBSD on the VAX-11/750.
In my humble opinion you should run a   | D | I | G | I | T | A | L |   Operating System on a VAX !

• VAX-11/750 Frequently Asked Questions by James Lothian
• VAX History
• VAX/VMS
• An other VAX-11/750

slot # VAX backplane - installed module list 1  empty - L0001 - Floating Point Accelerator 2  L0002 - Data Path module 3  L0003 - Memory Interconnect module 4  L0004 - UBI module 5  L0008 - PCS module 6  L0006 - RDM module 7  empty 8  empty 9  empty 10  L0016 - Memory Control module 11  M8750 - 1 Mb Memory module 12  M8750 - 1 Mb Memory module 13  M8750 - 1 Mb Memory module 14  M8750 - 1 Mb Memory module 15  M8750 - 1 Mb Memory module 16  M8750 - 1 Mb Memory module 17  M8750 - 1 Mb Memory module 18  empty 19  M9202 - UNIBUS out (to next backplane)  Note. Slot #1 is the most right slot!

At the left of the VAX backplane is a DD11-DK 9-slot UNIBUS backplane.
In slot #1 (at the right side), position A/B, is the M9202 module from the VAX backplane.
The non-used slots have an NPG / Grant Continuation module G7273 in position C/D. In the slots 3-4 and 5-6 are UDA-50 controllers installed (M7486 / M7485), which form two ports (A and B) for four RAxx disks per port. In slot 9 position A/B is an M9312 to terminate the UNIBUS.
In slot #1 of the VAX backplane (now empty) goes the floating point accelerator (FP750) module, L0001. I have that board, but I read that the L0001 is a small oven, so much heat is generated by this module! So, for now I have not installed that board.

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The VAX–11/750 control panel is on the front of the computer and has of the following indicators and switches.

• Seven indicator lights
• Power On Action switch
• Boot Device switch
• Reset button
• Five-position keylock switch

Indicator Lights
There are seven indicator lights on the control panel. The first three indicate the state of the computer. The remaining four indicate the state of the remote diagnostic procedures, if that option is available.

• Computer state indicators

  POWER	Glows green when power is supplied to the VAX.
  RUN	Glows green when the VAX is running.
  ERROR	When dimly lit, the VAX is running normally! When brightly lit, the VAX has detected an unrecoverable error. If an error occurs, push the white RESET button to reset the VAX. The ERROR light remains dimly lit. If the light is not lit during normal operation, the bulb is probably defective.

• Remote diagnostics indicators
  If the VAX has a remote diagnostic read-only memory (ROM), there are four additional lights on the control panel. These lights indicate the state of the remote diagnostic procedures. They are only visible when lit.

  REMOTE D	Glows green when the keylock switch is in the Remote or the Remote Secure position.
  RD FAULT	Glows red for 10 seconds when the VAX with a remote diagnostic ROM is turned on. This indicates that a selftest is in progress. When this light glows red for more than 10 seconds, the remote diagnostic ROM has detected an error in the remote diagnostic module.
  RD TEST	Glows amber when remote diagnostic tests are in progress.
  RD CARRIER	Glows green when the remote diagnostic center has established a connection with the console subsystem of the VAX.

• Power On Action switch
  The Power On Action switch has the following settings.
  

  BOOT	Boots the system from the drive selected by the Boot Device switch. This is the setting for normal system operations.
  RESTART	(boot) Attempts to restart the system. If the restart fails, boots the system from the drive selected by the Boot Device switch.
  HALT	Stops the VAX and displays the console-mode prompt (>>>) on the console terminal.
  RESTART	(halt) Attempts to restart the system. If the restart fails, stops the system and displays the console-mode prompt (>>>) on the console terminal.

  Set the Power On Action switch to BOOT during normal system operations.
  The setting of the Power On Action switch determines what happens after any of the following events.
  • The power is turned on.
  • A power failure occurs (and the contents of memory are not saved by the battery backup unit).
  • A shutdown occurs (if you entered "Y" at the auto reboot prompt).
  • The microprogram detects an error halt condition (for example, a HALT instruction executed in kernel mode).

• Boot Device switch
  The setting of the Boot Device switch tells the VAX which drive holds the system disk. The VAX checks the position of the Boot Device switch and tries to boot from the indicated drive in the following situations.
  • When you enter the BOOT command without specifying a device name.
  • When the system attempts to boot automatically.
  The Boot Device switch has four positions: A, B, C, and D. In position A the system boots from the console tape cassette drive. Positions B, C, and D indicate the controller designations for the disk controllers attached to your system. The VAX assumes that the selected drive has a unit number of zero on the disk controller designated by the Boot Device switch.
  If the system disk is on a local disk drive, set the Boot Device switch to the position that corresponds to the controller designation of that drive. If the system disk is connected to an HSC device, set the Boot Device switch to position A.

• RESET button
  Press the RESET button to shut down and restart the system. On some VAXen this button is labeled INITIALIZE.
  The way the system responds depends on the position of the Power On Action switch.

• Keylock switch
  The five-position keylock switch controls system power and determines how the VAX responds to commands from local and remote console terminals.
  

  OFF	Power is supplied to the battery backup unit and to the time-of-year clock, but not to the computer.
  SECURE	You cannot use the local console terminal in console mode to control the computer. You can use it in program mode as a user terminal. Pressing Ctrl/P has no effect. A |D|I|G|I|T|A|L| diagnostics center cannot use the remote console terminal when the switch is set to SECURE. Pressing the Reset button has no effect because it executes a console mode command.
  LOCAL	You can use the local console terminal in console mode to control the computer. A |D|I|G|I|T|A|L| diagnostics center cannot use the remote console terminal when the switch is set to LOCAL.
  REMOTE/SECURE	You cannot use the local console terminal. A |D|I|G|I|T|A|L| diagnostics center can use the remote console terminal in both console and program mode, but cannot use it for fault isolation. Pressing the Reset button has no effect because it executes a console mode command.
  REMOTE	A |D|I|G|I|T|A|L| diagnostics center is in control of the remote console terminal. You cannot use the local console terminal. However, the |D|I|G|I|T|A|L| diagnostics center can enter commands to restore control to the local console terminal.