Parallel to the physical PDP-11/70, here is a simulated version of it. It is photorealistic, written in platform-independent Java and connects to a modified SimH over network.

This SimH contains an extended PDP-11/70 CPU and logic to interface to the Java panel. So the simulated 11/70 can be controlled over the panel in a realistic way, and also displays the history correct light patterns.

Per default SimH executes RSX11-M. And yes: the famous "idle pattern" of RSX11M now appears on your desktop! (Like in this video of a real 11/70)

 simulated pdp1170

For the simulation I shot lots of photos from the real panel, then processed them with Photoshop. It is the same processing chain as described for the PDP-10 KI10 panel.


This PDP-11/70 panel simulation is very similar to the PDP-11/40 panel I made before. So this description page is essentially a link page to the 11/40 Blinkenbone project.

Download and install

Download is from GitHub, see here for detailed info.

To install, just unzip into an arbitray directory and execute the "pdp1170.bat" (or ".sh") batch file.

What's running?

After start, two separate applications run on your desktop: SimH and the panel simulation.

Both communicate over a network protocoll, so perhaps your firewall will ask wether some ports should be opened. Agree!

SimH executes a RSX11-M distribution, so you should be familiar with that OS. A basic PDF doc about RSX11-M is included in the archive. You operate the running PDP-11/70 through SimH's console terminal window as usual. Of course you can run any disk image on SimH by modifiying the "ini"-file.

The modified SimH implemenets an additional "REALCONS" device to control the panel, see here for details.

And the RSX11-M distribution was prepared by Mark Matlock, check out his article about RSX11M on SimH. He too connected a (blue!) PDP-11/70 panel to SimH with BlinkenBone, watch his video.

Operating the panel

Again, this is just a quick guide! The PDP-11/40 page contains more instructions and a little MACRO11 program, which shows a running light on the panel if keyed in correctly.

You operate the Java panel by just clicking onto the switches and the two knobs.

  • For a lamp test, click the unlabeled white switch.
  • To stop the simulation, press switch HALT. You'll notice that SimH goes to it's console mode, the simulation is stopped. To restart, release HALT and click CONT.
  • You can also single step through the RSX11-M code by pressing CONT while HALT is active. SimH will show the current opcode.
  • To manipulate memory, use the LOAD ADRS, EXAM and DEPOSIT switches.
    Of course, any experiments will ruin the RSX11-M code, causing any kind of evil things if you restart the CPU.
  • Beware: on the PDP-11/70, there are two selector knobs which influence the LED displays.
    For the "running light" program, the upper "ADDR SLECT" knob must be in the CONS PHY position, and the lower ADDR SELECT knob must be switched to DATA PATHS.
  • The both selector knobs react on left and right clicks.

For more info about the switches, see the DEC document "KB11C PROCESSOR MANUAL (PDP-11-70) (1975, EK-KB11C-TM-001).pdf" from the archive.
The console panel is described in "Section III Console". starting at PDF page 181.

Pro tip: Run this simulation on a monitor with touch screen !