Pidp-8: A Pdp-8 Minicomputer On Raspberry Pi

Made by Oscar Vermeulen

About the project

Everyone wanted a PDP-8 minicomputer. Well, in 1968. Blinkenlights! Just boot the SD image on a Pi, maybe add the front panel later on.

Project info

Difficulty:

Estimated time:

5 hours

Published:

25th July 2018

Items used in this project


Hardware components

OSH Park Custom fabricated PCB

The front panel PCB designed for the PiDP-8

x 1
Adafruit 40-pin header x 1
udn2981 driver IC x 1
Resistor 1k ohm x 3
390 ohm resistor x 12
Toggle switch

Any small switch works fine, but I made my own 'PDP-8 replica switch' for good looks.

x 26
1N4148 – General Purpose Fast Switching x 26
5 mm LED: Yellow

Any 5mm yellow LED

x 89
Raspberry Pi 3 Model B

Any Pi from the A+/B+/2/3/Zero will work. Bootable SD card image works on all of them except the 3. For the 3, install the tarball on Raspbian instead.

x 1

Story


Project goal: to create a faithful, low-cost replica of the PDP-8/I minicomputer (1968). Operated through a Blinkenlights front panel, it should bring back the user experience from the past. Replicating all stages in its development: from 1968 to 1979, from teletype & paper tape all the way through to hard disks and multi-user systems.

See my PiDP-8 web site for full details on the kit.

Why?

Why not? To illustrate how utterly unique the PDP-8 was in the evolution of computing. Born in the era of paper tape chewing, front panel programmed dinosaurs, it evolved all the way to running a proper operating system (even multi-user virtual machines!) from 10MB disk cartridges. It was pretty much the prototype of a personal computer.

How?

There's 3 stages to this project:

  • Software-Only: just boot the SD card image on your Pi. Note: only for the Pi 3, install the tarball on a standard Raspbian image. The Pi will boot up in 10 seconds as a PDP-8 terminal. Read the simh manual on how to operate it without physical front panel. Download link: bootable SD card (also runs on the hardware versions!)
  • Low-cost hardware hack: insert the Pi to the "Blinkenlights" front panel PCB and you have a fully functional hardware replica. Board can be made from the Gerbers by OSHpark, Seeedstudio, Elecrow or anyone else. Or buy it from me ($15, leave a message here).
  • Fancy version: I made this into a $145 kit, with pretty acrylic front panel, custom switches and bamboo case. See here (link) for details on when the next batch of parts is made.

Naked front panel PCB, or complete replica unit

What to do with it?

See here (link) for details. In summary: control the world, or play the very first video game (spacewar), or hook up 8 terminal sessions to run your company. It's a minicomputer... The PDP-8 is also an incredibly good way to learn about how a computer works at the lowest level. Because it is a very simple machine, yet has loads of good software.

Details:

Because a Raspberry Pi is rather more powerful than you need to replicate a PDP-8, it's dual-mode. Whilst the PDP-8 is running and blinking its front panel, you're free to use the Pi Inside to do whatever else you want to do with a Pi. Use it as a file server, VPN access point, or whatever. Just with a very blinky front end.

The PiDP will accept a classic serial terminal, or ssh terminal sessions from a modern PC. puTTY is fine, but a CRT emulator (cool-retro-term) is recommended to recreate the proper vintage atmosphere:

In case you do not have a vintage serial terminal: use cool-retro-term instead.

See my PiDP-8 web site for full details.

Schematics


PiDP user manual

See my web site for any updates

Kicad Project file, Inkscape front panel artwork, source code

See my web site for potential updates

Code


Actually, see my web site for future updates.

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