simh with BlinkenBone and PiPD11 extensions

This repository is a fork of simh/simh that integrates the following:

• simh: The Computer History Simulation Project
• BlinkenBone: extend the SimH simulator with real or simulated console panels
• PiDP11: recreating the PDP-11/70

Please consult the individual README and LICENSE files in the tree.

The BlinkenBone and PiDP11 sources have been reorganized and merged into the simh source tree (including changes to scp.c and the addition of REALCONS). To build with REALCONS support, build simh with USE_REALCONS=1; to build for PIDP11 (on a Raspberry Pi only), build with USE_PIDP11=1. The BlinkenBone and PiDP11 binaries can be built on Linux by running make.sh in the BlinkenBone subdirectory. Unlike Joerge Hoppe's original distribution, this builds only for the current machine (not cross-compilation).

The PiDP panelserver has been rewritten to use libgpiod (rather than directly manipulating device registers by mmap'ing /dev/mem). It works on both 32-bit and 64-bit systems. There are different source files for v1 (which, oddly, is the package libgpiod2) and v2 (package libgpiod3).

Panel servers for other machines (PDP-1, PDP-8, PDP-10) are yet to be written.

Build/update PiDP11 on Raspberry Pi

This has diverged from Oscar Vermeulen's PiDP11 installation and runtime scripts. It does not include the PDP-11 disk images.

To build on a Raspberry Pi, change directory to the root of the GIT repository and do the following:

cd BlinkenBone
./make.sh

On some systems you may need to configure the kernel variable dev.tty.legacy_tiocsti to 1 to allow the console to inject characters into the simh console input.

Build/install on Windows

Windows support is very brittle at this time. Nonetheless, if you want to try...

simh itself has good support for building and running on Windows. There is no supported version of Windows on the Raspberry Pi, so the PiDP panel simulators are not applicable. However, with some work it is possible to use simh with the Java panel servers.

Java is "write once, run anywhere", so you can build BlinkenBone/javapanelsim/panelsim_all.jar on Linux and run it on Windows with an equivalent JDK. To build it on Windows, install JDK 19 or newer and also install Apache Ant; then cd to the BlinkenBone directory and run make.bat.

The Visual Studio Projects folder contains a project file to build a PDP11 with REALCONS, but this has only been used with Visual Studio 2022. It creates the executable BIN/pdp11_realcons.exe If you need to rebuild it for an older IDE (particularly if you want to build for Windows XP using Visual Studio 2008), then you will probably also need to rebuild BlinkenBone/3rdparty/oncrpc_win32. Warning: there be dragons here...

There is no support for building a REALCONS-enabled PDP11 simulator using mingw64.

Installation

Installation runs on the build machine only at this time. From the root of the simh repository, do the following:

cd BlinkenBone
./install.sh

which does the following:

1. sysctl dev.tty.legacy_tiocsti=1
2. Create the user pidp11
3. Populate the pidp11 home directory with the script pdp.sh (which connects to the screen session) and add it to the .profile
4. Create /opt/pidp11 and populate it with client11, server11, getcsw, and pidp11.sh
5. Create an initial version of /opt/pidp11/systems containing idled.
6. Install the systemd service files and start the services

If you want the simulated system to share the Ethernet on your device, un-comment the following line in install.sh:

# setcap cap_net_raw,cap_net_admin=+ep ${PIDP11_OPT}/client11q

Major Changes Relative to the Upstream

client11 (simh)

Relative to simh, the makefile and sources have been updated with two additional environment variable options:

• USE_REALCONS=1: Include the REALCONS client support from Joerg Hoppe
• USE_PIDP11=1: Include REALCONS and an additional change for PiDP-11/70 support (see below).

If these are not set, the makefile will build all of the simulators the same as the upstream. On a Raspberry Pi, make.sh command in the BlinkenBone directory will build the PiDP11 variant of the pdp11 and rename it to client11.

The only difference for the PiDP-11/70 (USE_PIDP11=1) is the handling of a power switch event. The address select knob on the PiDP-11 generates this event, which indicates that the simulator should be restarted. For other REALCONS builds, this event causes simh to break to the command line with the quit command pre-populated.

server11

The PiDP-11 panel server has been rewritten to use the lipgpiod library instead of mapping /dev/mem and accessing the GPIO device registers directly. It can be run as a non-root user that belongs to the gpio group.

getcsw

This new utility replaces scansw. It reads the switch register from the panel server via the Blinkenlight API (rather than directly from the PiDP-11 GPIOs. There are some command-line options that control how the value is formatted.

systemd services

There are two systemd services:

• pidp11panel.service - runs the panel server (server11) under the non-privileged account pidp11 with group gpio and with the ability to set a real-time thread priority. Unlike Oscar's version, the panel server runs continuously (even when the client is restarted).
• pidp11.service - runs /opt/pidp11/pidp11.sh with a new screen under the non-privileged account pidp11.

/opt/pidp11/pidp11.sh

This script is the main client loop. It reads the switch register (with getcsw) and selects the system to simulate. Oscar's version creates a command script in /var/run to launch the simulation and also to control what happens when the address select knob is pressed. This version does not use an intermediate file; instead, simh uses the boot.ini script in the selected system directory. When the address select knob is pressed, simh exits. The simh exit status and behavior of pidp11.sh is:

• 0 if the RUN/HALT switch is in the RUN position: the process repeats (reading the switch register, selecting the system, starting simh)
• 1 if the RUN/HALT switch is in the HALT position: the script exits (which causes the pidp11.service to terminate)