It’s been a long time coming: the support for Oscar Vermeulen’s PiDP-11 console – in fact, I’ve been working on it, on and off, for over two years. Not that it was particularly difficult, but other things got in the way. The latest of those ‘other’ things was probably the worst so far – the […]

Stack limit

Some weeks ago I was involved in a discussion about how the leds on the 11/70 should work – more specifically, how to deal with the differences in the ‘real’ hardware and Oscar Vermeulen’s PiDP-11 console. I had what I thought was a rather nice idea, but it wasn’t received very well – and, given […]

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 […]

Things are moving!

Blinkenlights, for instance. It’s so hard to believe that it’s already almost been 3 years since my last post here. Well, I did have to hack my own site – I didn’t remember the admin password. Still, it’s not really like nothing did happen in the meantime, just nothing that I felt was finished enough […]


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 […]