Building and Using the PiDP-11 Emulator Kit

VOLUME WARNING - The music is much louder than the dialog. Sorry. I didn’t realize how much louder it was at the time.
I bought a PiDP-11 kit that allows you to recreate the PDP-11 experience using a Raspberry Pi 3 or 4. Watch me solder the components onto the board, assemble the computer, and use it via terminal software running on my TRS-80 Model 12. Believe it or not, I didn't make any soldering mistakes...though I did make some mistakes during case assembly, as-noted in the video.
I left more of the build footage in than originally planned, as this was a ton of work. Even at 3000% speed-up, it's a substantial portion of the video, and I thought it good to show how much work goes into these kits.
Links:
PiDP-11 web site: obsolescence.wixsite.com/obsolescence/pidp-11
Music: Disco Knights by Quincas Moreira
(Taken from the KZbin Audio Library)
Music: The Jam by Slynk & Mr Stabalina
(Taken from the KZbin Audio Library)
If you like to jump around, here's the index:
Intro (0:00)
Unboxing (0:57)
Painter's tape and the unpacking the components (3:17)
Sorting the components (4:09)
Soldering: Diodes (4:27)
Soldering: Resistors (4:59)
Soldering: Interface connector (5:52)
LEDs: Mounting and soldering (6:16)
Pushknobs: Mounting and soldering (7:58)
First test (8:10)
Keyswitch header, and MAX232 overview (9:59)
Keyswitch header, MAX232 and capacitors: mount and solder (10:51)
Ready for switches (11:16)
Switches: mounting and soldering(11:42)
The finished board (12:41)
Keyswitch and case assembly; soldering MAX232 TTL lines (13:19)
Connecting to the PiDP-11 via serial port (14:28)
Starting PiDP software and choosing an OS (16:50)
Booting BSD 2.11 and looking around (17:46)
BSD Network: PING and the HTTP server (21:41)
Booting Unix System V (23:12)
Playing Hangman and Monopoly...kind of... (24:57)
Shutdown and Outro (27:03)
I do these videos unscripted, so I apologize if the in-the-moment descriptions of things are a bit all-over-the-place. If you have any questions/comments about this video, you can find me in any of these fine locations:
The CoCoTALK! Discord Server
The TRS-80 Color Computer (CoCo) group on Facebook
The CoCo Crew Podcast group on Facebook
On the Vintage Computer Forums (vcfed.org)
The TRS-80 Models I-4/4P Group on Facebook
Tandy / Radio Shack Model II /12 / 16 / 16B / 6000 Owner's Group on Facebook
Thanks for watching!

[@TJBChris]

BE WARNED ABOUT THE VOLUME: The music in this video is louder than the dialog. A lot. I didn't realize this when I edited it. KZbin gives me no way to address it once it's uploaded. Also, this video was released in 2021, before I had invested in more professional audio equipment. So: Be warned. But also, there's no need to tell me in the comments. I know. Believe me...I know. If that's an issue, move on to someone who gets paid to do this. Love, -TJBChris

[@squirrelarmor]

I love it. Makes me miss my at&t 605s. =)

[@davidgari3240]

Amazing to see 30 years of blood, sweat and tears reduced to a 1/2 hour vid. Thanks. -David Gari -Living in a van down by the river.

[@davidgari3240]

Oh, and I was a BSD man from the git go, but System V started to turn my head.

[@TJBChris]

I started out on Sys V, so BSD took a bit of getting used to. Thanks for watching!

[@hongkongcantonese501]

Everything about this video is gold. The audacity of the project. The choice of music. The documentation. Subscribed.

[@alanb76]

Looks like fun. I started on a PDP-8 and used the PDP-11 with early Unix at UCB. Then built systems with LSI-11's for science. Fun stuff.

[@TJBChris]

It was a blast to build. This was my first hands-on experience with a PDP-like system. Thanks for watching!

[@mistie710]

To be honest, I'm less interested in UNIX distros for the PDP-11 than I am for older native systems such as RSX or RSTS/E. Good looking 11/70 mock up though.

[@randomdestructn]

Some unnecessary negativity in these comments. Good video, thanks for the build and demo.

[@TJBChris]

Thanks for watching! I thought it was a worthwhile project. It’s a fun way to play with a PDP-11-like system.

[@billymania11]

Pretty cool. I guess it's a way to experience the original UNIX in all it's glory.

[@pkhoury1212]

Thanks for this video. I acquired my late friend's PiDP-11 after he passed, and I'm eager to play on it. On that note, I also have an actual microPDP-11/73 that I've wanted to play with (archived a working copy of RSX11 from the ST-412 that was inside), but obviously, the PI version is much more versatile.

[@TJBChris]

It’s a fun little machine for sure. I’ve always been curious about PDP systems, but never enough to try to own a real one. The PiDP-11 gives me the best of both worlds. Thanks for watching!

[@pkhoury1212]

@@TJBChris I picked up some MicroPDP-11's a few years ago and I'm keeping one, but I like the smaller footprint of this PiDP-11.

[@bobdole57]

Ive got a pidp-8, pidp-11 and an altair duino arriving Wednesday.

[@TJBChris]

Enjoy! They are fun to assemble and fun to use. Thanks for watching!

[@AndrewErwin73]

I think it is a bit surreal that the Pi 4 is more powerful than a room full of PDP 11's... but hey, I want one too!

[@jessepollard7132]

I understand the PiDP4 is About like the unreleased PDP-11/74 (a quad processor prototype). And I want one too. I used to program PDP-11/45 and PDP-11/23 systems for navigating seismic surveys at sea. Even the PDp-11/45 had (at one time anyway) a dual processor implementation. Dec never sold many. and the PDP-11/74 was cancelled as some of the bean counters thought it would compete too much with the VAX/780. (PDP-11 performance was quite outstanding at the time- I unerstand the Micro pdp-11/73 was actually faster than the VAX/780 though I never got the chance to use both at the same time. (the VAX was pretty good - but he bus architecture was horrible no faster than about 10MB/sec data transfer and made paging performance rather poor.

[@AndrewErwin73]

@@jessepollard7132 Very nice. QUITE JEALOUS!

[@tcpbox]

It is really surreal, bacause I have 4 Pi 4, 1 Pi 3 and 1 Pi 2, 2 lDell's laptop one I7 the I5, but I want to have a PDP 11. Why I do not have one yet?

[@kerryedavis]

I read somewhere, I think it was for the PiDP-8/i kit, that it's smart to get a small-diameter metal rod that will pass through all of the front-panel switches - maybe at the hinge point? to use as a guide while soldering them in. That keeps all of the switches aligned and looking good. Hopefully that's doable for the 11 as well.

[@TJBChris]

Interesting! At the time, I hadn’t come across that, or I probably would have tried it. Fortunately it came out well. Thanks for watching!

[@SudzBud]

Nice project

[@inerlogic]

That's cool... i built the Briel 8800 micro and the High Nibble Imsai 8080.... i should get this to add to the collection.... you know what would be awesome though? Sound leveling your voice with the montage music.....

[@TJBChris]

Thanks for watching. In later videos I’ve been lowering the music volume; I edit these videos on a laptop, so the differences in volume weren’t apparent to me until someone pointed it out. It’s not perfected yet, but I am aware and trying. This is a hobby for me, so my videos won’t be meticulously produced like the pro KZbinrs. Appreciate the feedback, though, and thanks again for watching!

[@davidgari3240]

Yes, I watched the entire build (while typing this). Pre-emptive multi-tasking Rules !

[@TJBChris]

I've enjoyed reading your playing-along commentary! :D

[@battleangel5595]

Ordered my kit the other day. Already have a Pi ready to go. My soldering skills... "I know what I'm doing. I think. Therefore I am probably right." in my best Red Green impersonation.

[@TJBChris]

Good luck, it’s fun to build! My soldering skills are also amateur at best. Enjoy!

[@battleangel5595]

@@TJBChris I'm 29 years rusty. But I'm looking forward to putting this kit together.

[@kdietz65]

Great fun.

[@Drew-Dastardly]

JFC. The jazzy elevator musak was at least 20dB louder than your narration. I could forgive the terrible choice in musak alone if it was just played a lot more quietly. Just a tip for future videos.

[@keyboard_g]

Yes, I am deaf now.

[@TJBChris]

Thanks - the issue is the older videos like this one just are what they are at this point. I’ve been editing these on a laptop, so the difference isn’t always as noticeable to me while editing as it is for folks with headphones or larger sound setups. I’m an amateur KZbinr for sure…no Patreon so it’s all on my dime. 😀 That said, in more recent videos I’ve been working on the sound levels and I recently bought a wireless mic system so my voice levels are uniform and should be more in line with any music. This video seems to get more comments about the audio than most, so I’ll update the description to provide some warning. As to the choice of music: it’s deliberately cheesy. 🤣 Thanks for watching!!

[@derekchristenson5711]

Very cool!

[@pwbarrett7]

How could they make the rotary-switch pressable for reset - I thought they were going for accuracy. Why not the halt/load/start toggles?

[@SharkoonBln]

The music is a little bit on the loud side, I had to adjust speaker volume every time you change from voice to music and vice versa. Other than that, it´s a nice video and a cool project.

[@TJBChris]

Thanks for letting me know. I edit these videos on my laptop, so the difference in volume wasn't obvious to me. In the future I'll have to dial back the music for the time-lapse sequences.

[@SharkoonBln]

@@TJBChris Thanks in advance. On laptop speakers the difference may be not as obvious, so you are forgiven ;)

[@BentYetti]

too loud for me too. Unfortunately unwatchable on my system due to music rattling my everything lol. Looks interesting though.

[@stephenleclaire2319]

I enjoy your channel though the finer technical aspects go beyond me. I worked with a PDP-1170 on a space surveillance project atop Haleakala Maui in the early 80's. Remember the boot sequence and the MCR code.

[@TJBChris]

Thanks for watching and for the feedback! This channel is really a look at my journey trying to learn some of the deeper technical detail on all of these things. I'm getting there, but there's still a ton to learn. The PDP-1170 space surveillance work sounds fascinating on both the PDP and the space front!

[@paulstubbs7678]

Nice build, when fitting serial ports where the device itself (Pi etc) only supports 3 wire operation, I tend to either loop the handshaking lines back, RTS-CTS etc, or if 12V is available, connect the outgoing lines to that, so that when you connect to a terminal/PC etc, that supports a fully implemented serial port, all is happy. Usually the TTL to RS232 adapter boards you buy for Arduino's etc, have the 9/25 pin connector on a PCB, so why they don't do something more sensible with the handshake lines has me scratching my head, it's only a few extra tracks that costs nothing extra to produce during mass assembly.

[@TJBChris]

Thanks for watching! I’ve always wondered why these TTLRS-232 boards don’t do the fairly simple additions needed to make pickier serial devices happy. Even some serial-to-Ethernet converters lack support. I suspect that so few devices even care about CTS/RTS these days that it’s not even given a thought. The TRS-80 II/12/16 line are the first systems I’ve had that were unforgivingly picky about it. Most other systems, even my other TRS-80s, either don’t care by default or can be made to not care fairly easily. I guess that’s part of the fun, right? 😄

[@pkhoury1212]

@@TJBChris I thought of adding in a MAX232 to mine, but I'm starting to opt more for using a Keyspan USA19HS, which I've successfully used with Linux/Raspian in the future. Any comment on those? Obviously, they're a bit bulkier than the MAX232 solution. Also, if I do get a MAX232, what part number did you order? Your bag in the video looked like it came from Mouser...

[@TJBChris]

@@pkhoury1212 You’re right, I’m using the MAX232. I haven’t had any issues with it. My Tandy systems seem to have no issue talking with it, but I’d bet there’s more than enough room in there for the Keyspan solution. I hoped I had the part # floating around in my e-mail, but I’m a serial deleter of messages, so I don’t have it handy. If I can find it in my orders I’ll reply back.

[@TJBChris]

Found it. I ordered the MAX232 from DigiKey. When I ordered it, the part # was 296-27963-5-ND, described as MAX232EIN according to my order. Good luck!

[@pkhoury1212]

@@TJBChris Thanks for the part number. And 0.1uF caps, right? Or does that part require 1uF? The keyspan solution is definitely bulky, but does work so far.

[@SusanAmberBruce]

cool

[@systemBuilder]

Where did you find a pidp11? I'm looking for one, thanks.

[@TJBChris]

You can find the kit I built in this video here: obsolescence.wixsite.com/obsolescence/pidp-11. Thanks for watching!

[@markgarrett8963]

what was the paul simon’s reference?

[@TJBChris]

I was doing a bad job referencing “You Can Call Me Al”. I’d say it wasn’t my best work, but most of my references in videos are dad jokes at best. 🤣. Thanks for watching!

[@davidgari3240]

OS/2 !? Sign me up!

[@TJBChris]

OS/2 is where it's at! I loved OS/2 and was a big believer back in the day.

[@KameraShy]

Use a muffin tin to sort out all those little parts. Keeps them from rolling around.

[@kwccoin3115]

Pdp was used to learn BASIC and Cobol, plus resume printing. Never play any game as you have lots of people waiting behind you. It seemed my pineApple II (fake copy) is better.

[@davidgari3240]

termcap? Awesome but Noooo!

[@ste76539]

WHy did you use an 8Gb RPi to emulate a 1970's 16 bit computer? More money than sense?

[@TJBChris]

I’ll give you the same answer I give everyone when they ask “why” I do anything. The answer is “because I can”. It wasn’t expensive (at the time, at least, no idea what it’d cost today). And because someone created the kit and I was interested. Haven’t you done something others would consider frivolous because you enjoyed it? We all have our priorities, on which we’re willing to spend money. 😁

[@Drew-Dastardly]

He can use an 8GB RPi4 for the development then get a cheap ass 1GB model to keep it running. That's the beauty of the plug and play RPi system. Of course not accounting for the chip shortage.

[@lawrencedoliveiro9104]

There are people still alive (like myself) who used these old machines when they were new. And who appreciate the part they played in getting us to where we are today.

[@statinskill]

You missed the point in this entirely altogether. I had a real nostalgia moment when I sat down to an interesting VM/CMS session that was the same release I used as a kid when my dad would sometimes take me to work. Nobody is going to use a PDP-11 today to get work done. Unless they're actually still supporting PDP-11 systems that are active today controlling railway systems. Of course mostly with the hardware emulated. So many reasons to emulate an older machine on modern hardware.