Comment by DonHopkins

I just made a PDP-7 and Type 340 vector graphics display emulator that runs in the web browser, based on SIMH, in order to reincarnate and run 128 pages of PDP-7 assembly language source code listings of a CAD system called PIXIE written at Cambridge by Heinz Lemke.

It also boots PDP-7 UNIX, the one this article is about. Log in as ken, password ken:

https://hyperties.org/cabinet/unix/

Same cabinet runs DECUS DUEL (the spacewar), DEC's light pen test, a lunar lander, and guess-the-number, besides PIXIE and the Forth below.

Here's a music video I cut from the 1969 films of that system running on the PDP-7 and Titan at Cambridge. PIXIE has the first known radial menus:

https://www.youtube.com/watch?v=jDrqR9XssJI

Cambridge librarian David Chapman digitized the uncut films from the Cambridge University Library:

https://www.youtube.com/watch?v=j9R63T2xGCA

https://www.youtube.com/watch?v=lCrl5QmQ9aA

The listing the emulator runs was assembled 12 February 1972. I wanted to look and feel first hand how the radial menus work, so here's that code running in the browser:

https://hyperties.org/cabinet/symelec/

Here's the PDP-7 assembly source code I recovered. The page runs the image it assembles to:

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

I asked Mitch Bradley, who is the Forth guru who wrote OpenFirmware, if there was a Forth system for the PDP-7, so in one day he and Claude created one, including a Turtle Graphics library for the Type 340 vector graphics display! It turns out that the PDP-7 instruction set is perfect for Forth, and its inner interpreter loop is only three instructions.

Mitch Bradley's PDP-7 Forth:

https://github.com/MitchBradley/pdp7forth

How Mitch's Forth works, and my enhancements (full names, CREATE DOES>, PIXIE rings):

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

Video demo of PIXIE and FORTH on the PDP-7 Cabinet Emulator with the Type 340 Vector Graphics Display:

https://www.youtube.com/watch?v=lo8kdY-5i6c

It's easy to make virtual real and fictional PDP-7 devices that, like the actual Type 340 vector graphics display, plug in custom IOT instructions and even perform DMA, like a Turing Machine co-processor, the Ultimate Machine (Minsky's design, which Claude Shannon built, that just turns itself off), and a Data Hand (like VPL's Data Glove) that tracks your hand with the webcam:

Turing Machine (adds IOT instructions and uses DMA to run TM programs out of 18 bit core memory, which it animates with Forth turtle graphics and Type 340 display character generator):

https://hyperties.org/cabinet/turing/

Forth Turing Machine driver and renderer:

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

Ultimate Machine (adds IOT instructions to control and monitor device that turns itself off, and animate it with Forth turtle graphics):

https://hyperties.org/cabinet/ultimate/

Forth Ultimate Machine driver and renderer:

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

Minsky and Shannon's Ultimate Machine (sometimes called Useless, but Marvin considered it Ultimately useful):

https://en.wikipedia.org/wiki/Useless_machine

Data Hand (adds IOT instructions to read hand position, orientation, and pose, and draws hand with Forth turtle graphics):

https://hyperties.org/cabinet/hand/

Forth Data Hand driver and renderer:

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

Ultimate Machine + Data Hand = Ultimate Hand (combines the above devices into an interactive Ultimate Machine that lets you turn it off with your own hand, animated with Forth turtle graphics):

https://hyperties.org/cabinet/ultimate-hand/

Forth Ultimate Hand demo putting it all together:

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

The Type 340 was a real PDP-7 device. Shannon's box was a real box, and the DataGlove was a real glove, but neither was a PDP-7 peripheral. These are virtual devices that plug in the way a real one did: their own IOT instructions, and DMA.

Here's the manifesto about the emulator design:

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

>We control the horizontal. We control the vertical. The machine in the page is ours, all of it at once: every register, every word of core, every device, and the host around them. Nothing here is a black box we have to squint at through a keyhole. So when something would be better, we make it better, from whichever side is closest. The 1960s machine stays honest. Everything around it is ours to invent.

Cabinet Design:

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

>The rule throughout: instance first. Hardwire what SYMELEC needs, comment where the abstraction would go, generate it lazily when a second instance demands it. Work backwards from the software you want to run.

Cabinet README:

https://github.com/SimHacker/WillWrightShowForFood/blob/main...

>An emulator: a stand-in for a cabinet, so the original program can run. PDP-7 is the first plug-in instruction set, for PIXIE. Type 340 on a canvas, light pen as a hit-test.