PiDP-1 Rack SN 225 - Up and executing

[bgreat]

I love the kit. This was an exceptional build.  Thank you!

I've had it running for a few days and in testing. I already have plans on how I intend to expand the operation. I am a glutton for punishment... no cross compiling... I plan on all my work being on the "real" hardware current minimal implementation.

My number one project will be a working paper punch and reader. I just need to decide if it will be full size or to scale. Any thoughts?

A quick review of the group shows there are other "hardware" efforts in process. Mag tape and drum storage is intriguing as a future upgrade. I need to explore the PDP-1 hardware history in more detail to decide my upgrade path.

Enjoy!

Bill

[Glenn Babecki]

Bill (b great),

While I haven't really gone down the rabbit hole regarding recreating paper tape peripherals, I would highly recommend not scaling the reader and punch for two reasons.

First and foremost, you at least stand a chance of finding standard 1 inch paper tape by keeping the devices standard sized. There are various discussions on PiDP related forum threads about people searching for paper tape.  I can't find one particular reference right now, but I believe there is a source related to some aeronautical application.  If I come across the reference to the paper tape source I'll pass it along.

Second, it will be difficult enough designing and constructing a standard size reader and punch.  There are also a few forum threads of people musing about recreating the punch head.  You can glean the potential issues for those discussions.

Since the reader and punch are likely to not be in close proximity to the console, I see no need to scale it down.  A punch and reader are not ridiculously large anyway.  Scaling a device may initially sound appealing, but after a certain point you encounter a threshold of the thing not being usable by human hands.  There also can be mechanical and aesthetic issues as witnessed by the inability to fasten all the nuts on the PiDP-1 switches due to the close proximity of the scaled switch positions.

Just some random thoughts off the top of my head, and really more my personal perspective.

Regards,

Glenn

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[Matthias Barthel]

Bill,

Congratulations to your build 👍 have fun !

I'am also a friend of working with real hardware, i build a backplane for the pidp1 to connect real hardware to the pidp1, its wotk in process but the most features works realy good. I also attempt to build a papertape reader and puncher to store my programs on paper like in the old days 🙃

You can find some information about the backplane here in the group and some Videos on YouTube ( https://youtu.be/2yzoHX5kaec?si=-yFlu00XmlPj77LY )

Matthias 🙋🏼‍♂️

To view this discussion visit https://groups.google.com/d/msgid/pidp-1/CAL1sX6nvJ_7F-%2BeMnnXJzyHuN0TP6V3h9_rgB6fr4zRBZ9eifg%40mail.gmail.com.

[Glenn Babecki]

Bill,

For what it's worth, I found the forum thread regarding paper tape sources.

https://groups.google.com/g/pidp-11/c/a9ZD9R5OhXY/m/OMaX_0GyAwAJ

At the end of thread there was the following reference to a source of paper tape.

https://www.hermieusupply.com/en-EN/flight-strip.html

This appears to be the best source for fan-fold or roll formatted paper tape.

The tape is intended to be used with a thermal printer, which may have interesting consequences in of itself, but I'm sure it can be punched.  I didn't see if there were any specs about the thickness of the tape, but suspect that it should be consistent with traditional paper tape.

Glenn

[bgreat]

I’ll check it out.  I’ve had difficulty finding sources.

Enjoy!

Bill

[Clem Cole]

There are numerous reader designs/products you can find via an Internet search, and you can either build them yourself or purchase one already built.   The bigger issues are two-fold: creating a working punch and then finding a supply of 1-inch (25 mm) paper or Mylar to feed it.

Other than restoring an old ASR33, so far I have not seen a realistic punch made, althought I have seen a few where the punch was harvested from old equipment and interfaces with a microprocessor and local circuitry to splice a punch on top (I used to have a colleague who interfaced a paper tape reader he found and Eli's in Cambridge).

But assuming you have a punch, feeding it will be difficult as most 1" paper sources have adhesive on the back.  I believe if you look for paper tape for NC machines, you might find it, although many of those used mylar for durability.  The last time I tried to find it, I was able to find a source in the UK: https://www.jrw.co.uk/store/index.php?main_page=index&cPath=24   I believe there is a French firm Hermieu Supply that makes 1" fan fold   called https://www.hermieusupply.com/en-EN/flight-strip.html

Good luck.

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[Matthias Barthel]

This guy https://hackaday.com/2025/06/23/building-a-custom-paper-tape-punch-machine/

Build a papertape-puncher, the plans are available on his github, he had also a cutter to make 2 rolls of 1" papertape out of one thermal roll.

The puncher is my next project in line .

Matthias 

To view this discussion visit https://groups.google.com/d/msgid/pidp-1/CAC20D2NH9Bu6dgmewn8wQAj%3DBnc6Z3wT4JT3aREdJVaurTjD8w%40mail.gmail.com.

[William Greathouse]

He’s using thermal paper rolls cut down. A bit light weight compared to punched tape standard. It is a starting point. 

Enjoy!

Bill

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Please excuse any typographical anomalies as this email originated from a mobile device.

On Dec 8, 2025, at 15:02, Matthias Barthel <maklumatp...@gmail.com> wrote:



[Malcolm Ray]

I'm fortunate enough to own both a tape punch and reader, but I haven't yet tried interfacing them to any of my PiDPs, partly because tape is scarce! Particularly the DEC-style fanfold.

One alternative I've thought about is using a cheap receipt printer to print black circles, to mimic a tape. This could then be read optically.

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[R H]

I’ve been thinking about the same approach using a cheap label printer (coz I bought one recently to, umm, print labels).  It seems a “P12” printer can print on continuous thermal paper which is 12-15mm wide… which I’m guessing would be around 47-59% scale of a 1 inch paper tape?

I love the look of the original PDP-1 paper tape reader with some great looking curved metal guards and was thinking about making a PiDP-1 scale model of one using some metal paint sprayed 3d prints; I need a simple project to learn OpenCAD etc and this seems a good starter project.

For the reader itself I might try to use the same analogue approach that this one uses; https://e-basteln.de/computing/papertape/overview/

Cheers, Richard

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