The PDP-11 was probably the most influential computer design ever. And in 1975, the 11/70 was the last to sport a proper Blinkenlights front panel. In red and purple. Sorry, Rose and Magenta, these were the 70s. But then - all of a sudden - front panels were gone from our lives and we were forced to look at dull beige boxes for the next few decades.
The really fascinating thing about this computer though, is that it is quite usable even today. You can run a proper networked unix or go back further in history and run Unix v6 whilst you study the famous Lions Commentary. It can do vector graphics, works as a web server...
The PiDP-11 project aimed to bring back this venerable machine. With front panel. There might be a Raspberry Pi hiding inside, but thanks to the simh emulator it is fully compatible. All the original operating systems and loads of programming languages and software come pre-installed, ready to boot. You can even hook it up to 5 real serial terminals if you like.There are actually four stages in this project you can consider:
- run the PDP-11 emulator on your Raspberry Pi and explore historical operating systems & software;
- add the PiDP-11 circuit board to add a 'Blinkenlights' front panel;
- solder switches onto the circuit board to gain control of the machine over the front panel;
- or buy the complete replica kit with fancy case, acrylic front panel cover and custom switches.
When emulating the PDP-11, the Pi has plenty of power left to do all the other things you would normally do with a Pi (media server, file server, etc). The PiDP is both a PDP-11 and a Pi at the same time.
To get a front panel, you could buy the complete PiDP-11 kit (and you're welcome to do so), but this being Make, here we describe the cheaper, more industrial-looking Do It Yourself option. Send the Gerber PCB design files to any PCB shop and solder up your own Bare Bones front panel. A PCB would cost a bit less than $15 per unit, in quantity five, from places like jlcpcb.com.
Including parts, $30 gives you the full Blinkenlights of the original PDP-11. Add the 30 required switches (any switch with the standard Mini Switch footprint will do) and you can also take control of the PDP-11 in the old style. The best style. Not from the terminal, but toggling in Octal code and single-stepping through whatever program you want to debug...
The Raspberry Pi sits at the back of the board and does all the work.
That work includes simulating the PDP-11, but also providing original I/O (RS-232 serial terminals) and modern replacements (networking, terminal sessions over ssh/wifi, Tektronix 4010 vector display simulation on HDMI or VNC). And there are dozens of disk and mag tape images to simulate all the storage peripherals. Here are some of the pre-installed operating systems:
The PDP-11 used the famous Unibus to attach to all sorts of hardware - from paper tape readers to hard disk packs and laboratory instruments. The Unibus is emulated inside the PiDP-11, but any modern I2C chip or module can be brought into the PDP-11 as a Unibus peripheral! The idea is that the PiDP-11 could be like an Arduino, just slightly bigger and with proper development languages like FORTRAN or MACRO-11 ;)
Even crazier: attach the UniBone card, and that can plug in to a real PDP-11 Unibus. Taking over any of the real PDP-11 peripherals becomes feasible, even using the physical core memory of the donor machine.
(Note: when you download the Gerber from the link at the top right, it saves as a .zip.txt file for some inexplicable reason. Just rename it to a .zip file.)