PDP2011 Overview

This website describes PDP2011 – a re-creation of the well known series of PDP-11 computer systems in VHDL. Everything that is needed to run a PDP-11 system is included; you can run a complete PDP-11 system with console, disks and other peripherals on a simple low cost FPGA development board. The original V5-V7 versions of Unix, BSD 2.11, and DEC’s operating systems for the PDP-11 from DOS/BATCH to RSX11mp, all work as they do on the real hardware.


  • You can configure PDP2011 to be 11/03, 11/20, 11/23, 11/34, 11/44, 11/45, 11/70 or 11/94. This also sets up 18- or 22-bit memory management, special instructions like MARK and MTPS/MFPS, EIS instructions, and FIS or FPU. The model specific instructions and the most important differences between the system models are implemented to the point that many of the original MAINDEC test programs run without error.
  • PDP2011 can drive a PiDP-11 console.
  • There are disk controllers for RK, RL and RM/RP disks; these use SD cards to store the disk image on.
  • The system can be hooked up to a network; it includes a DEUNA compatible Ethernet frontend for the ENC424J600 Ethernet chip (as on Digilent’s PMODNIC100); you can run DECNET on RSTS and RSX, or TCP/IP on 2.11BSD. Or instead of the ENC424, you can use ESP32 for wireless networking with TCP/IP.
  • The PDP2011 project includes a terminal core to interface to a VGA screen and PS2 keyboard; you can combine it on the same FPGA you run the PDP-11 system on, or run it on separate board. You can configure the terminal to be a vt100 or a vt105.
  • Up to four serial ports can be configured for the console, additional terminals, links to other systems etc.
  • You can build up a complete MINC laboratory system – all original MINC modules for A/D, D/A, clock, digital input and output can be configured, and there are lots of extras to drive sensor hardware to connect to the A/D component. There is even a vt105 version of the embedded terminal that lets you display the MINC waveform graphics.

Known problems and limitations

  • The RH controller for the RP/RM disks only support 1 disk drive.
  • The wireless network esp32 frontend does not currently support native DECNET.
  • The original RL distribution disk for RT-11 V5 crashes on boot. Everything works if you copy the distribution to RK though, and earlier versions work fine as well.

Future plans

  • Hardware to support the MINC peripherals.
  • Fancy front panels and casings to display the whole thing – from a basic 11/70 blinkenlights to a full-on MINC with all I/O available.


The copyrights to the VHDL referenced on this site are held by me. There is a more detailed copyright notice in the download archive; in short, you are allowed to run the core for personal use, but you can not use it commercially.