Munching Squares

On a PDP-7 from 1964. Turn sound on.

Exhibit A:
The Type 340 XY display has a P7 phosphor has a slow decay which gives Munching Squares an eerie afterglow. Both programs read the left switches to modify patterns. A small AM radio was used to pick up RFI from the Type 347 controller. For the MIT AI lab hackers the Munching Squares "music" was referred to as Munching Tunes.
Exhibit B:
ADDB 1,2
ROTC 2,-22
XOR 1,2
JRST .-4
HAKMEM (MIT AI Memo 239, 1972) Item 146 reports that it was written for the PDP-1 by Jackson Wright in 1962.

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10 Responses:

  1. James C. says:

    The phosphor decay makes the munching much more trippy. The patterns are fascinating, reminiscent somehow of a Persian carpet. Given that Phosphor is already a thing, hopefully someone will be inspired to hack it together with Munching Squares to recreate the original PDP-7 + Type 340 experience.

  2. Glaurung says:

    1. Mainframes are loud.

    2. PCs used to be really loud too. Thank goodness they aren't any more.

    • jwz says:

      I think you missed that the "loud" was coming from a nearby AM radio. So this was them being loud in spectra you can't normally hear, but yes.

      • Glaurung says:

        Was talking about the massive fan noise at the start of the video before it focused on the screen. And the vintage workstation startup sounds you have for your screensaver videos. Noisy, noisy fans, noisy hard drives.

        • ssl-3 says:

          I dunno, man. The ceaseless grunt of the ball bearing power supply fan and the hollow clatter of a stepper-driven headstack in a girthy MFM drive, before the floppy drives hammer themselves home reminds me of simpler times.

    • Jeffrey W. Baker says:

      Mainframes are loud but a PDP-7 is a minicomputer, taking up only most of a room instead of several rooms, and weighing a mere half a ton.

      • tfb says:

        I suspect loudness is relative: I bet PDP-7s were fairly noisy too, assuming they had fans at least (maybe they didn't?)

  3. Bob says:

    in news from less distant times (yeah I am old enough to have had the line printer play music)

    So sorry, there is a Nickelback song in there...

    But there is an airwolf to make up for it:

  4. Zippington J. Whatsis says:

    "It was tricky, but..."

  5. My original XScreenSaver munch was a ripoff of a DarkSide of the Mac module, a shareware screensaver akin to After Dark. (I think it could even run AD modules.) I had read the Jargon file and knew about munching squares, although the descriptions never quite lined up.

    As I remember it, DarkSide's had two modes, one which was a solid color per square and one of which changed color on every pixel. Both DarkSide modes munched one square at a time, then cleared the screen. I didn't like the color-changing one, so I made it do multiple squares. I don't remember when it started doing multiple squares at a time. I wrote it on 256-color graphics hardware and just decided to take the color-map starvation effect as an extra feature of the hack.

    I knew about Munching Squares from the jargon file, but I didn't know about super-slow decay PDP-1 monitors, so the DarkSide version was the closest one I'd seen. The Jargon file had some comments about XOR, so I tried doing that, and I kind of liked it.

    Years later I ran into a video that showed the original hack, and I was a little disappointed I hadn't gotten it right. Obviously, some enhancements are in order.

    Also, smoking clover:

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