What is QBone?
QBone is a fascinating project by Jörg Hoppe. It is based on a PDP QBus module that can be inserted into any QBus backplane. It implements all features required by the QBus, so this module looks like any other QBus module from the PDP11 perspective.
The module integrates a BeagleBone Board (BBB). This is an ARM-based modern computer, like Raspberry PI. The biggest advantage of BBB over Raspi is: that the board contains two separate I/O processors called PRU (Programmable Realtime Unit). They execute code at 200 MOps, have own GPIOs attached and are especially built for doing bit-banged protocols in software. They can replace FPGAs in medium speed-applications. (text taken from Jörg Hoppes site)
With QBone, it is possible to develop code running on BBB that emulates a PDP11 device, and even more, a complete PDP environment.
This is the main goal of the QBone project.
QBone allows to add virtual devices to a PDP11, and to run a mix of real and emulated devices all together.
Moreover it is possible by emulating also the CPU module, to run a complete virtual PDP11 with devices, but still being attached to a backplane and for example testing a single physical device.
The possibilities are endless. So I decided to buy a QBone Kit. QBone comes as a finished module or a DIY kit where the SMD parts have been presoldered.
While QBone is for QBus, there is also another project UniBone, which is for Unibus. There is also another project called QProbe that allows to trace the QBus more in detail and that has LEDs for all the bus signals. Marvellous.
Both projects share the source code on Github.
Product page - http://retrocmp.com/projects/qbone
Source on Github - https://github.com/j-hoppe/QUniBone
Google Group - https://groups.google.com/g/unibone
Building the QBone Kit
Not too much parts to solder. Only complicated thing is the soldering of the BBB connectors onto the QBone PCB.
Some intermediate state of soldering the parts:
Final state (so far):
BeagleBone pin headers
My environment for testing
I have an unused H9278-A backplane. This can take 8 quad-sized modules. It is capable of addressing 22 bit addresses. For doing the acceptance test for QBone, I used this empty backplane. It offers also bus termination option, and in my backplane, the bus terminators are present.
H9278-A backplane connectors: See e.g. BA23 Enclosure Maintenance, Order Number EK-186AA-MG-001, section BA23 System Interconnection Pinouts
Hello World Module
My first uses of QBone
First I’ve checked a broken M8044 PDP11 RAM module.