It all started with the great PiDP-11/70 kit developed by Oscar
PiDP-11:RECREATING THE PDP-11/70.
First, the PiDP-11/70 kit was built. But after some time playing with the PiDP-11/70 placed on the wooden base, I wanted more ...
The wooden base was not to my personal liking (sorry Oscar), and cables at the open rear side was not "great" either.
Slowly, the idea of a scaled PDP-11 system rack got shaped. The PiDP-11/70 had to be "boxed", just like a real PDP-11.
However, I must say that the real PDP-11/70 was never available in a single BA11-K box (19 inch width, 10.5 inch high).
The real PDP-11/70 was always in a BA11-F "box". I hope you forgive this distortion of reality.
So, what is presented here?
Realized constructions, ideas that are almost finished, ideas that are almost ready to be realized, and crazy ideas.
Challenging, but fun ...
- PiDP-11/70 in a box
This is realized and finished! The PiDP-11/70 front panel is attached to a box made of aluminum plates
and "L" angled aluminium profiles.
Inside the box is a small 180W PC power supply. For the rest this project was basically just adding
a metal box to the PiDP-11/70 front panel.
The rear side of the box has a fan for ventilation and a panel for external connections
such as the HDMI output, ethernet RJ45 socket, four USB connections, and two I2C sockets for control of external devices ...
- RK05 disk drive
I have to admit this was a crazy idea, but it is finished! It was my intention to create a working replica of the RK05
disk drive (at 60% scale of course), to match with the PiDP-11/70. And when I say replica, I mean that down to the details of
a real RK05j. The door looks like the real thing and it has a working lock/unlock mechanism. I could have chosen the easy model,
the RK05f. The RK05f has a fixed disk and therefore does not have a front door, but that is the only (visual) difference.
However, that door is where most of the work went into, because if you have a door, you must also have scaled RK05 cartridges
as the removable storage media ... Nevertheless, for an easy way out, the RK05f is described as well. No, there is not a rotating platter
nd read/write heads. Instead of magnetic recording, a USB stick is hidden inside the "RK05 disk pack". When the pack is mounted (in exactly
the same way you would mount an RK05 pack on a real RK05 drive, a USB socket clicks magnetically and makes the connection. As a modern USB
stick can hold so much information, there is a second USB socket (also magnetically locking) that uses the 4 USB wires as a 3-bit coded
switch, realized as a 3 bit DIP switch inside the "RK05 disk pack". The pin header defines which "disk file" is selected when the pack is
mounted. Saves on 3D printing disk packs. You still have to "swap" he disk pack, but it is the same disk pack that you load, after changing
the DIP switch.
- RK11-C indicator panel
RK05 disk drives are normally connected to UNIBUS or QBUS with the RK11-D or RKV11-D controller,
respectively. However, before the RK11-D controller the RK11-C controller existed. The RK11-D consist of 4 quad-sized modules in a
dedicated 4-slot backplane, The RK11-C consists of many Flip Chips in a dedicated backplane. But the RK11-C included an indicator panel
with 144 lamps (!), and in real-time you can see which attached drive is accessed, the memory address for the data, which "address" on the
disk is accessed (side, track number, sector number), error bits, etc. As this looked like a simple project (no moving mechanical difficult
parts), I made a front panel design and created an interface for driving 144 "warm-white" LEDs. A test program written in Phyton with a
graphical user interface using wxPython proofs that it works! Clicking with the mouse on the graphical presentation on the screen actually
controls the corresponding LED on the indicator panel. Patching SIMH's pdp11_rk.c is a "work-in-progress" ...
- Papertape reader "PDP-11 style"
On the PiDP-11/70 mail list was a discussion about reading papertape. If you have a real PC05, you actually can connect that to the
PiDP-11/70 (I built a PIC-based interface for that). And then you can read *and punch* tape. But the PC05 is big compared to the
PiDP-11/70. So, the discussion was about papertape readers through which the papertape was pulled manually. That was not good
enough for me, so I started to collect ideas how I could build a papertape reader "D|I|G|I|T|A|L style". I guess
that at this moment (March 2020), I have all major issues solved, or at least think I can find a solution and realize a new crazy project.
Update (August 2025 ... time flies). The idea of creating the tape reels made of aluminium was discarded, because the cost of making one
tape reel would go over 100 Euros (that was even for me too crazy). But nowadays 3D printing is a "piece of cake", and after making a rough
sketch with dimensions, a collegue at work drew the 3D design and printed the rear disk, the part for holding the paper tape, and mounting
the reel on a motor shaft, and the front disk with nice openings for looks and aid to get paper tape threaded onto the shaft. At the moment,
I am working on a 3D printable parts that will hold the FPA100 9-channel emittor and receiver. Plan is to finish this project this year.
- TU56 tape drive
This must be, by far, the most crazy idea, and probably the most difficult one too. Using Front Panel Express I designed a 60% scaled
TU56 front panel. The read/write head is tricky, but I think that the ones I found on eBay might work. Real DECtape is wide, but when
you scale the width to 60% it is close to 0.5 inch. That is the width of standard magnetic tape! The trickiest part will probably be
the tape path. Just like the RK05, I want to be able to actually store data on and retrieve data from the tape. But this time it is
really magnetic tape. An "easy way out" would be a USB stick, and simulate the reading/writing by spinning the motors, moving tape
over the head, but nothing more. It is an "escape option", but I want to try actual writing/reading first ...
- LPS-11 unit
I chose this unit to be on my list for several reasons. First, it has a nice looking half-height front panel with knobs, connections
and a six digit red LED 7-segment display. Another good reason to choose this unit is that you can actually connect "things" to it,
provided that it works ... But this project is last on my list, so that will not be "real soon now".