NSWIT aka CHSNCP

[larsbrinkhoff]

There is a PDP-11 Chaosnet router/terminal concentrator called NSWIT, or New Switch. It's similar to MINITS, but older. NSWIT may have started at MIT, but was later mainly in use at the S-1 project at Lawrence Livermore National Laboratory (often called LLL). There may also be some connection to the Plasma Physics TV system, see #1837. NSWIT has support for both the "MIT keyboard" (probably Space Cadet) and SAIL keyboards.

I believe the MIT copy was in the CHSNCP directory. We have some scraps of files from there, e.g. NSWIT 106 and 276.

We do have a full set of files from SAIL:

• [SW,CBF] - plain NSWIT by @cbf66
• [GRN,CBF] - with Grinnell support
• [NCP,CBF] - with Arpanet NCP support
• [1,EAK] - another copy by @eak

I tested assembing NSWIT.PAL[SW,CBF] and that went fine, both with ITS' PALX, and the one in [1,EAK].

I believe NSWIT was often run on an LSI-11, and was probably started from RT-11.

[larsbrinkhoff]

RT-11 installation guide by @dugoh: https://gunkies.org/wiki/Installing_RT-11_5.3_on_SIMH

@cmgauger advises to use RT11DV50.ISO.zip from http://pdp-11.classiccmp.org/RT-11/dists/

[larsbrinkhoff]

The set of files in [SW,CBF] seem to come in a few different flavors: ASWITC and BSWITC, which are quite simple, and then NSWIT with three configurations: L0, L11, and L29. Out of the latter three, L11 is most complex and requires code for Chaosnet and a mysterious Unibus device called "Newman".

I wonder how these five relate to this host table snippet. The GATEWAY (aka "ARPANET 11"?) ought to be the even larger configuration with Arpanet NCP code from [NCP,CBF]. Maybe GSWIT is the [GRN,CBF] code, aka "Grinnell 11". L11 has the Chaosnet address 10405, same as S1-NSWIT.

HOST S1-A,		1/95,SERVER,WAITS,PDP10,[S-1,S1,S1-COPROLITE]
HOST S1-B,		2/95,SERVER,UNIX,VAX
HOST S1-C,		3/95,USER,,PDP11
HOST S1-GATEWAY,	[0/95,CHAOS 10404],USER,,PDP11
HOST S1-GSWIT,		CHAOS 10403,USER,NSWIT,PDP11
HOST S1-LSWIT,		CHAOS 10400,USER,NSWIT,PDP11
HOST S1-NSWIT,		CHAOS 10405,USER,NSWIT,PDP11

[larsbrinkhoff]

I sent @emooreatx a zip file with NSWIT L0 and ASWIT for testing on a real PDP-11.
FYI @dseagrav

[larsbrinkhoff]

I'm reading the code, and I now have the impression that "Newman" is a multi-processor shared memory. Each processor can map in two or four windows from this memory into its Unibus address space. They can also interrupt each other.

[larsbrinkhoff]

I made this a draft pull request. In lieu of the "real" CHSNCP files from MIT, I have used the [SW,CBF] files from SAIL. Some additional files from [NCP,CBF] were needed to build the NSWIT L11 configuration. Maybe the NCP fileset is more up to date, but for starters this is good enough to experiment with.