Fun with dpys5

[Bill E]

Other than just letting it boot from tape, you can control some fun bits. It's actually 3 different display progs in one. It has munching squares, the default snowflake, and Minskytron. Note the snowflake isn't quite the same as the standalone snowflake.

So, how to use it?

Load it, snowflake should start.  Then:

Squares - set the address to 0, test word to 400 (octal), press start.

Snowflake - (default) set address to 10, press start, no config via test word

Minskytron - set address to 500, test word to 677721, press start

Fiddling the test word for squares and Minskytron change behavior drastically. The above settings will get you a display, then you can fiddle if you want. Enjoy.

Bill

[Bill E]

Also, Minskytron only checks the test switches on start, so restart if you want to change the settings. Squares reads the switches constantly, easy to play with. For Minskytron, try 477721 to see how dramatic the changes are.

[Oscar Vermeulen]

I need to write more details about the demos in the manual. Mainly to refer to Norbert Landsteiner's definite write-up: https://www.masswerk.at/minskytron/ (scroll down a bit). An index to all his PDP-1 pages is sorely needed for PiDP-1 users to discover them all. 

[Norbert Landsteiner]

Munching Squares adds a constant factor in the test word to the value in the accumulator, does some XOR bit operations and splits this into X (lower 9 bits) and Y (higher 9 bits) coordinates. – Just start and play with the test word switches (which are read anew for each iteration, so it's interactive).

Snowflake runs on its own without further input (but the stand-alone version has a few display option on the sense switches).

For details see here: https://www.masswerk.at/nowgobang/2019/snowflake-archeology

The Minskytron reads 3 sets X and Y factors for 3 oscillators from the test word on start and then runs on its own.

Each X and Y factor is made up of 3 bits, so there are Y1,Y2, Y2, X2, Y3, X3 on the test word from left to right, each 3 bits/switches.

While it's a rather short program, it's actual workings are pretty complex. It's kind of visual synthesizer, but probably more of a network feedback explorer.

This was probably written just when Minsky finished his paper "Steps Toward Artificial Intelligence" – so there's some plausibility to the latter interpretation.

I've an unfinished, rather extensive blog post on the "Minskytron" lying around.

(What may there to to be said about a few lines of code? 😀)

This also includes an extended version (by me), which allows to produce even more patterns and variety.

Source code and binary (octal) here: https://masswerk.at/spacewar/sources/minskytron_ii.zip

The unfinished and unlisted blog post is here (which also allows to play with the Minskytron, including the "Minskytron II" extensions for changing the operator inside the oscillators, which are mapped to the sense switches in the extended PDP-1 version): https://masswerk.at/nowgobang/2023/minskytron

The playground can be found here (direct link): https://masswerk.at/nowgobang/2023/minskytron#playground

(This also allows to switch to a 24-bit resolution – just as the never-built PDP-2 would have featured. Switching to the higher resolution, patterns that have dissolved into "snow" in 18-bit resolution often reappear!)

Please handle links to that blog post with discretion.

On Thu, Sep 18, 2025 at 8:54 AM Oscar Vermeulen <vermeul...@gmail.com> wrote:

I need to write more details about the demos in the manual. Mainly to refer to Norbert Landsteiner's definite write-up: https://www.masswerk.at/minskytron/ (scroll down a bit). An index to all his PDP-1 pages is sorely needed for PiDP-1 users to discover them all. 

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