The smallest PDP-11 ever!

62.5 by 25mm. That is how big the smallest ever PDP-11 system is, based on the CYC1000 FPGA board from Trenz Electronic. It’s not a small PDP-11 though – it is a full PDP-11/70 with PiDP11 front panel console, RH70+RP06 disk, DEUNA ethernet controller, and two serial ports. Ok, it is a bit bigger if you connect all that, but still smaller than all the other boards I’ve worked on so far.
The FPGA is Altera/Intel’s latest generation Cyclone, and it is pretty fast – it runs the CPU of the PDP2011 at 12Mhz. There is an FTDI chip that is used for programming the board; it can be used as a console port as well. And a 8Mbyte SDRAM chip, 8 leds, two really tiny buttons, a 2×6 pin row suited for connecting PMODs … exactly what we need to run PDP2011 on!
To make connecting the PiDP11 front panel easier, I have designed a ‘shim’, a small board – also 62.5 by 25mm – to be mounted under the FPGA board. It maps the GPIOs to the side of the FPGA board to a 40 pin header for the PiDP11 panel, and a 2×6 pin header for an extra serial port.

If soldered together, it is small enough that the whole thing will nicely fit into the PiDP11 case, and the back panel will still fit. I don’t think that will be the case if the two are connected with sockets… but, since the CYC1000 is also the cheapest board I’ve seen so far, I don’t think sockets are really needed.
In the next weeks, I will write up a howto for the boards, and add the bitstreams for the FPGA to the download page. I haven’t made up my mind if I will be selling the shim (maybe even as a kit with all the headers you’d need) or if I will just publish the gerbers so everyone that wants one can order from their favourite PCB shop themselves. If you’re interested in either option, let me know – that’ll help me make up my mind!


Barry November 12, 2019

I would like to make one of these as soon as all the details are published.
An alternative to publishing the Gerbers is to share the shim project on PCBWAY and then people can just get them manufactured as they want them and shipped to anywhere in the world.

Martin T November 16, 2019

Wow! This looks to really be the perfect PDP-11/70 – great work!
I personally would prefer to buy either;
* The PCB-shim and all connectors as a complete kit.
* The whole thing: Altera board ready programmed, and with shim fitted (just ready to plug-in to the PiDP11 case and turn on power)

Faye April 2, 2020

I’d like to get the shim and connectors as a kit, I’ve managed to source the Cyc1000 in 25kle form, as well as the pmodsd and pmodnic100. My only real experience
with FPGA so far is the lovely MiSTer on the de10nano (Cyclone V) but I managed to solder to a Pi Zero without destroying it…

MiSTer got me thinking about all the old computers I’ve used and the PDP11/44 holds a special place in my heart as the first distributed computer system I used. I’d love to see
edt, cobol77, ingres, jcl/rsx/rt11 etc. again, maybe introduce a new generation to it.