Booting 11/70

Booting a PDP-11 is something that I have maybe overlooked a bit, in trying to approach the ‘real thing’. In the history of PDP2011, it’s not that long ago really that I added the M9312 boot roms option – and I really still prefer my own boot code. Partly because PDP2011 can be different models […]


After the summer, I’ve picked up work on the interface to Oscar Vermeulen’s PiDP11 console – what was left to do was the virtual settings on the address rotary switch and the actual values on the address and data lights. It mostly works now, and I’ve come to the point that I need to take […]


Finally, I’ve managed to find the time to finish up the new boot code, test everything, generate new bitstreams for the download page, and update the site.

There are now two different sets of boot roms to choose from. The sources in m9312l46.mac and m9312h46.mac are the – now almost unchanged – DEC M9312 boot […]


Last November, Scott Swazey asked why I made my own boot loader instead of using the original M9312 code.

I knew that the sources for M9312 were available, and I did have a look at them a long time ago. At that point, I was not sure I would ever get the CPU running, let […]

Fixes for DEUNA

Over the last months, I had a couple of occurrences of the problem where 2.11BSD would loose it’s network connection, reporting that there were no transmit buffers available on the DEUNA. All in all, I’ve seen this problem three or four times over the last year, but maybe ten times in the last month or […]

RSX11M-Plus. Finally.

A couple of weeks ago someone mentioned that there were some FPGA related articles in the December issue of Circuit Cellar. So I checked it, and one of the articles pointed me to the built-in logic analyzers that the leading tool chains now all seem to have. At least, the Circuit Cellar article is about […]


Last week Al Kossow posted some new sources for XXDP tests on Bitsavers. Included are the sources for the MMU tests for 11/34. I tried to run those, and was surprised by a list of error messages… Turns out, there were a number of issues left in my MMU implementation, that none of the other […]


Since DEUNA works, I more or less constantly have one or more boards running 2.11BSD. One of these has only been down twice since November 2 – the first time after three months when I accidentally touched the power switch while cleaning, and the other time last week when a transformer exploded across the street […]

DEUNA works!

Terasic's de0 board with Digilent's pmodnic100 attached

I already posted that I was working on it, so it should not be a very big surprise. DEUNA now works. At least, it works good enough for 2.11BSD – and very stable as well. I’ve even written a new web server for 2.11 – well, you’ve […]

PDP2011 has been to VCF

Jack Rubin sent me this picture of his DE0 board running RT11 in front of a real PDP11/70. Taken during the VCF East 8.0, which took place last weekend. It’s something of a classic ‘old meets new’ picture – there being something like 40 years of age difference in it. Would have liked to be […]