Running PDP10/KLH10 on Raspberry Pi

copied from Keith Halewood's facebook note 7/7/2019

https://www.facebook.com/notes/dec-computer-users/running-pdp10klh10-on-raspberry-pi/394084557900778/

This is a bit of a work in progress so beware the rough edges.

The PDP-10 (KLH10) distribution from github seems to have been modified to make it more general purpose so the various bits of documentation on the net seem to be a little out of date or confusing, so here’s how I got it to work so that I could install the Panda distribution of TOPS-20 onto it, along with DECnet (connection to HECnet) and TCP-IP. LAT too, was a bit of a surprise.

Firstly, the raspberry Pi. I’m running the minimal ‘buster’ version with a WIRED network. I have also used ‘apt-get install’ to install the following:

screen
bridge-utils
uml-utilities
autogen
autoconf
build-essential (if on minimalist install, such as debian, for example)
 

The Pi’s networking configuration has a fixed IP address so I’ve switched off the standard dhcp client and I rely entirely on the content of /etc/network/interfaces. For me, the contents look roughly like:

auto lo br0 tap1 tap2 tap3
iface lo inet loopback
iface eth0 inet manual
iface tap1 inet manual
pre-up ip tuntap add tap1 mode tap user simh
iface tap2 inet manual
pre-up ip tuntap add tap2 mode tap user simh
iface tap3 inet manual
pre-up ip tuntap add tap3 mode tap user simh
iface br0 inet static
bridge_ports eth0 tap1 tap2 tap3
bridge_fd 0
address 192.168.x.y
netmask 255.255.255.0
gateway 192.168.x.a

where x.y and x.a are the host addresses of your pi and default gateway. ‘simh’ is the userId of the non-privileged user under which you run your simulations. What has been set up here is a bridge device linking the real ethernet device eth0 and pseudo devices tap1, tap2, tap3 - usable by SIMH and by the PDP10 emulator.

Download and unzip the KLH10 emulator:
$ curl -L https://github.com/PDP-10/klh10/archive/master.zip > klh10-master.zip
$ unzip -o klh10-master.zip

Go into the ./klh10-master directory and edit the configure file. Find the CFLAGS setting and change the -O3 into -O2

Go back up a directory level.
Create another directory, say klh10-build and go into it and:
$ ../klh10-master/autogen.sh

Assuming you’ve installed autogen, autoconf etc., you should see a few files and directories magically appear in your current directory (klh10-build).

Type:
$ make
and watch it building the kl, ks and ks-its models in the appropriate subdirectories. You should see the compiler compiling with -O2. This is important. The -O3 optimisation seems to mess up something critical in the simulators.

Go into the bld-kl directory and you’ll see some executables like:
dpni20, dprpxx, dptm03, enaddr, kn10-kl, udlconv, uexbconv, vdkfmt, wfconv, wxtest.
Copy these to a location where you’ll be running the simulator with a configuration file and disc image file(s).

kn10-kl is the simulator executable. When running a simulation, it’ll fire up instances of dprpxx and dpni20. The dpni20 executable will need to be setuid root, ie:
# chown root:root dpni20
# chmod u+s dpni20
It’s annoying because the whole point about ‘tap’ network interfaces defined above is that a non-privileged user, ie. simh as defined above, should be able to exert full control over its side of the device.

WORK IN PROGRESS
Panda distribution of TOPS-20 , installation and configuration - see

 http://www.ldx.ca/notes/tops-20-notes.html

Talk about the workaround for the network connection and the fact it doesn’t use the tap device you want it to.... etc...
NCP might take a while to start... or not.
Using screen to let you detach the pdp10’s console...
Connections via TCP/IP, DECnet. LAT appears to work much better than DECnet’s CTERM.

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