I’ve just added a new release of PDP2011 to the download page. This new release contains several bugfixes and also new functionality.

Base system

  • The RH disk controller used to only work with RP06 images. It now also works with RP04/RP05, RM05, and RP07. Also, it supports the Setasi/Shelby RP12 RM06 layout of 64 sectors, 32 tracks that will work with RSX-11MPlus for disk images up to 2GByte, and a synthetic 64 sector, 64 track drive that works with 2.11BSD. The controller still only supports one disk drive at a time though (and I don’t think I’ll fix that soon).
  • Images for the ‘artificial’ drive types (RM06, RP2G) can be created by a modified version of simh that supports the new drive geometry. This has been tested up to a size of 2Gb (larger will not currently work). I haven’t published the required (relatively minor) changes yet, but will try to do so soon.
  • The serial link driver did not work very well if it would receive short stop bits from the other end – potentially leading to garbled characters. It should now be lots more stable and capable of higher speed. The issue was analyzed by Steve Falco (thanks!).


  • MINC now supports up to 64 A/D channels; the A/D channels present on the board are the lowest numbered channels, and all higher numbered channels are available to insert values into MINC that are obtained from other sources like sensors, other types of A/D converter, computed data, etc – as long as they more or less fit in a 12-bit signed integer.
  • All MNC module types can be configured to the maximum the software can handle: 1 MNCAD, 2 MNCKW, 4 MNCAA, 4 MNCDI and 4 MNCDO. That means 16 DA channels, and 64 digital input and output channels – plus some control signals.
  • The logic in MNCDI for detecting state changes has been corrected; the previous version would only detect rising edge changes.
  • A driver for the PMOD DA4 (Analog Devices AD5628-1) has been added, next to the PMOD DA2 that was already available.
  • A driver for the PMOD NAV (Microchips LSM9DS1 and LPS25HB). The digital barometer in LPS25HB will likely feature in a future project for a weather station.
  • A driver for the PMOD HYGRO (TI HDC1080). The temperature and humidity sensors will also be useful for a future weather station.
  • A driver for the PMOD COLOR (AMS TCS3472). This sensor allows to determine the color temperature, and hence elegantly establish if the sun is shining or if there are clouds.
  • A driver for the ADXL345 accelerometer that is present on the DE0-Nano boards.


  • The terminals now support double width and double height characters.
  • Automatic XOFF/XON has been added, and a bug has been fixed that would result in the receiver code to become stuck on overrun.
  • The terminals now support character attribute resetting in the VT200 style. This helps when using the terminals with current software that uses reverse video and assumes a VT200+ type terminal (like most Linux setups do).
  • A bug has been fixed that caused the first character on a new line at the bottom of a scroll region to be replaced by a blank.


Good June 9, 2021

how to connect qbus devices???

sytse June 9, 2021

That depends a bit – do you mean real, physical qbus devices? you don’t – the bus in PDP2011 is not directly compatible with either qbus or Unibus. But you can definitely use devices that are built into PDP2011, and those do not necessarily have to be Unibus or qbus. If the device doesn’t do DMA, there isn’t that much difference between the two busses at the logical level.

Is there a specific device on your mind?