Shim logistics

When I started the shim design, I hadn’t really thought about logistics at all – but sort of assumed that if people were interested, I’d mail them a shim and maybe the connectors too. The first prototype run of the board worked nicely – and my first beta tester was able to get it […]

Shim design (2)

So, picking up from where I ended up in the last post – basically, waiting for inspiration on how to best address the lack of elegance of the DE0nano + shim + PiDP-11. I did try several things – I made a lot of nice colourful 40-pin ribbon cables, different ways of folding and […]

Shim design

I was thinking back on the spring of 2017, and first time Oscar came over to my home and showed his PiDP-11 prototype. Already then the subject of a ‘shim’ came up… but we didn’t really reach a conclusion. Nor did we on later meetings…

It all seems so simple. The PiDP-11 has a […]

New but the same

One of those things I’ve postponed for years but now finally done – migrate my old server running Fedora 20 to something new. It turned out to be a mix of surprisingly easy and surprisingly difficult. The wordpress migration for instance turned out to be easier than I thought – but, the new version […]

The smallest PDP-11 ever!

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 […]

A possible issue with SDHC

The new SDHC capable RH controller works great. I’ve mainly used it for 2.11BSD so far, and everything works faster, more responsive, and nicer with it. Compiling the kernel, playing with Ingres – no problems at all. But this little command line:

while true; do /usr/games/fortune;echo;echo;sleep 2;done

after a random number of fortunes bombs out […]


It’s been a long time coming, but I’m happy to announce that I have finally finished SDHC support. Ehh, well, just for the RH/RP06 though. And the RH still only supports just one disk. The reason it took so long is that besides just adding SDHC I’ve also redone enough of the disk controller that […]


As a byproduct of the PiDP-11 console support, I’ve defined a more or less ‘standard’ pin layout for the 40-pin connector on most of the Intel/Altera/Terasic FPGA boards – obviously carrying all the signals for the console itself, but also for the most basic peripherals that all PDP2011 systems need: a serial port for the […]

RSTS and J-11

Some time ago, Paul Koning contacted me about the issue that RSTS did not correctly detect the CPU type when the cpu was configured as a J-11 type – 11/84 or 11/94. He had already identified a problem in the cpu sources: the MFPT instruction would set the CPU code in the primary register […]

FPU and DEUNA fixes

Since I found the problem with the BAE register in the RH70 that prevented RSX-11MP from running, I’ve been working on straightening out the timing between the CPU and the main memory. It’s nowhere near finished, but the first tests show that when it is, the CPU will be capable of much higher speed – […]