Replica of the PDP-1: PiDP-1

The PiDP-1 comes out of a loosely organised group of computer history hobbyists. In various cooperations, we did a PiDP-8, -11, and last year, a PiDP-10. They all share the idea of being a 'computer history capsule': a functional replica that should provide a realistic experience of how it felt to operate these historical machines, with their Blinkenlights - front panels - to debug, monitor and even program them. But also, with a curated software archive built-in that preserves as much of their software history as possible.

The PiDP-1 is done different in one respect - the simulator underneath still runs on a Raspberry Pi, but simulates the original system on a much lower level, that of the circuitry. It makes the simulation much slower. But then, the original ran at the equivalent of 0.2Mhz, so speed is not an issue.

But there is a purpose for this level of simulator detail: once you 'get' the PDP-1, you'll see it is a great retro platform for demo coding. There is fun to be had with running the world's first computer video game, spacewar. Some of the original graphics demos are enjoyable, as is playing around with the historical software tools that have been preserved. Nevertheless, hacking together a simple graphics demo or backporting a modern video game is very satisfying.

With the PDP-1 team at the Computer History Museum, we want to invite hackers and democoders to look at the PDP-1 - with the best of their code being run on the only real PDP-1 still alive at the CHM. With that goal in mind, we better make sure there is absolute fidelity in the PiDP-1's simulation...

Project Logs

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A PDP-1 Agent? A hacker replicant!
Oscarv • 10/04/2026 at 12:44 • 0 comments

For computer history preservation, might replicant Hackers become as important as replicas of their machines?
We replaced the old AI features with a full-fledged Hacker Replicant that you can install as an add-on onto the PiDP-1:

You can now install Agent-PDP1 as an add-on to the PiDP-1 (or, of course, any other Linux machine). This project gives you an old MIT hacker sitting next to you as tutor, guide, programmer. It has access to typewriter, front panel, and can see the Type 30 display. We suggest you call him Ben, for historical reasons.
Living with Vintage Lisp
Oscarv • 07/02/2026 at 21:23 • 0 comments

Or maybe, experiencing Vintage Lisp. The PDP-1 Lisp had a remarkable origin story. Not only was it quite a feat to get any Lisp on a machine as puny as a 4Kw PDP-1, the REPL concept was invented along the way too. By Peter Deutsch, at the time a high school student who got himself behind MIT's PDP-1.

The odd thing is - it is quite enjoyable to use even today. Once you figure out the little front panel intricacies. We did a write-up here:

https://obsolescence.dev/pdp1-lisp-introduction.html
A 1960s PDP-1 Cyberdeck
Oscarv • 03/12/2026 at 22:41 • 1 comment

A picture of the setup Angelo and I used this week for a PiDP-1 development sprint:
This was our home base for a great week. Bill Ezell has added cool things like drum storage and character generators to the PiDP-1, we had work to do. Also, the leftmost PiDP-1 can be seen with only 12 bits active. This is our new easter egg in the PiDP-1: it has a hidden PDP-5 mode starting next week.

Due to Mike Hill coming to visit with a very intriguing 4 instruction Blinky demo program:
PDP-5 coding on the PDP-1 is reasonable
Paleogaming!
Oscarv • 02/18/2026 at 19:53 • 0 comments

Before retrogaming came paleogaming. The video and terminal games written before the arrival of the microprocessor (yuck) - they are known by name by gaming history enthusiasts, but not many have tried them. Spacewar, Lunar Lander, Star Trek, the original Colossal Cave and Adventure.

We want to add a paleogaming mode to the PiDP-1, where all of these games boot up quickly, ready to play without any setup hassle. Work starts in two weeks. It will require PDP-10/11/8 and even Whirlwind simulators installed in the PiDP-1 innards, and some simh scripting to make it all work flawless.

But then, we will look at the PiDP-1 as the one and only paleogaming console :-)

To be continued!
The first batch of 200 has gone out!
Oscarv • 09/29/2025 at 01:35 • 0 comments

Well, almost. We're shipping 5-6 PiDP-1s per day at the moment, working our way through the waitlist of daring early adopters. Thank you, all of you! We really, really appreciate the confidence.
Now, we're waiting for parts to make the next 300. Over on the PiDP-1 Google Group, the fun has started. So far: a new disassembler, a new cross-assembler, a Forth and a Lisp (in Forth amazingly) have been written, plus a toolbox to inspect and convert paper tape images.
We've gotten Lisp to work, and the standard development suite of Expensive Typewriter (oops, Symbolic Tape Editor in DEC's own words), MACRO and DDT.
And work is underway to hook up modern I2C peripherals.
We're having fun! You do not need to have the PiDP-1 hardware to join in, the virtual front panel version works just fine on a Pi, Linux laptop or even Windows WSL2: PiDP-1 Github repository. Please come and join the fun. Plenty of software archaeology left to do (who will bring up FORTRAN?)
Making a pretty case out of PCB panels
Oscarv • 08/08/2025 at 06:28 • 0 comments

I think this little video is interesting for more than just vintage computer fans: it shows how we made a very complex-shaped case out of just PCB panels. It took a lot of experimentation (see earlier log posts) but it works extremely well. The end result is a case that is so strong, you can drop it from 5 feet on a concrete floor. We tested that, although not on purpose.
Here is the video:
...And look further down in the log posts for technical details. Perfecting this trick saved us a small fortune (which the budget actually did not allow for) compared to other case-building techniques like injection molding (yuck).

Meanwhile, we're busy packing up the first 200 kits :-)
It's done! We're making PiDP-1 kits
Oscarv • 08/06/2025 at 05:06 • 0 comments

It took much longer than expected, because of recurring logistical trouble. There's a lot of parts in the PiDP-1, and that made it a real logistical nightmare. Custom-designed aluminum profiles were one challenge.

But: It's done. We started making PiDP-1 kits today!
Here is the smaller of the two variants we designed, the PiDP-1 Console, Does it look like a retro games console? That is the plan. We're starting to write some new games for the machine. The type 30 vector display is very fun to code for.
So, the hardware development has come to an end. Now comes the real fun: reviving the 1959 PDP-1 with a hopefully active community of users and programmers. For the latter, we're writing a book. "Democoding on the PDP-1: A gentle introduction". Because this was the original democoders' machine, and if it is up to us, it will be again.
Into production! And book publishing?
Oscarv • 06/22/2025 at 15:59 • 1 comment

An update - all parts to make 200 PiDP-1 kits have been ordered. We were forced to use sea container shipping to keep costs under control. Things like the custom aluminum frame are heavy - but so is shipping all the PCB parts for 200 kits: the case is constructed from FR4 PCB material, giving a nice chunky weight to our little replica - but alas, shipping spoils the fun a little bit :-)
We're now focusing on polishing up the software, and on writing a PDP-1 programming manual. Ambitiously called "Democoding for the PDP-1: A Gentle Introduction". Four of us started making some appealing graphics demos with fully commented step by step source code. This will be fun!
Finished the first test batch of 5 machines
Oscarv • 04/05/2025 at 18:03 • 6 comments

In other words, we increased the number of PDP-1s ever produced by 10% in two days :-)
Lots of polishing up still two do. We're hiding from the world for two weeks to get it all done. Probably <i>almost</i> all done. <i>Mostly done.</i>
Spacewar controllers and Feature Creep
Oscarv • 03/15/2025 at 01:04 • 0 comments

So, we want to make the PiDP-1 a very affordable kit to make. Because, the more affordable the more chance that it will find its way to young coders who want to try their hand at PDP-1 programming!

But we're battling feature creep, we'll just have to add two spacewar controllers. The idea is to make it them tiny, low-cost PCBs that will do the job on their own, but at the same time, can be the PCB inside a proper custom-made wooden spacewar control box. As the original ones were all quite visibly one-off jobs too, a proper spacewar controller must look - artisanal.
But for those who do not like to tinker, they can use the PCB as-is:
As we had 36 extra IOs for lights or switches, we did spend the whole day thinking of other exotica to add. For instance, the three PDP-1s that made it onto Arpanet had extra button boxes - the time-sharing operating system used them to hook up multiple Teletypes.
But we decided against such things, they can all be done in software and the kit is already a package of 15 PCBs as it stands. And though PCBs are cheap, it does add up.