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!