For something that has been around since the 1930s and is so foundational to computer science, you’d think that the Turing machine, an abstraction for mechanical computation, would be easily understood. Making the abstract concepts easy to understand is what this Turning machine demonstrator aims to do.

The TMD-1 is a project that’s something of a departure from [Michael Gardi]’s usual fare, which has mostly been carefully crafted recreations of artifacts from the early days of computer history, like the Minivac 601  trainer and the DEC H-500 computer lab. The TMD-1 is, rather, a device that makes the principles of a Turing machine more concrete. To represent the concept of the “tape”, [Mike] used eight servo-controlled flip tiles. The “head” of the machine conceptually moves along the tape, its current position indicated by a lighted arrow while reading the status of the cell above it by polling the position of the servo.

Below the tape and head panel is the finite state machine through which the TMD-1 is programmed. [Mike] limited the machine to three states and four transitions, each of which is programmed by placing 3D-printed tiles on a matrix. Magnets were inserted into cavities during printing; Hall Effect sensors in the PCB below the matrix read the pattern of magnets to determine which tiles are where. The video below shows the TMD-1 counting from 0 to 10, which is enough to demonstrate the basics of Turing machines.

It’s hard not to comment on the irony of a Turing machine being run by an Arduino, but given that [Mike]’s goal was to make abstract concepts easy to understand, it makes perfect sense to leverage the platform rather than try to do this with discrete logic. And you can’t argue with results — TMD-1 made Turing machines clear to us for the first time.

In today’s digital era, we almost take for granted that all our information is saved and backed up, be it on our local drives or in the cloud — whether automatically, manually, or via some other service.  For information from decades past, that isn’t always the case, and recovery can be a dicey process.  Despite the tricky challenges, the team at [Museo dell’Informatica Funzionante] and [mera400.pl], as well as researchers and scientists from various museums, institutions, and more all came together in the attempt to recover the Polish CROOK operating system believed to be stored on five magnetic tapes.

Originally stored at the Warsaw Museum of Technology, the tapes were ideally preserved, but — despite some preliminary test prep — the museum’s tape reader kept hanging at the 800 BPI NRZI encoded header, even though the rest of the tape was 1600 BPI phase encoding. Some head scratching later, the team decided to crack open their Qualstar 1052 tape reader and attempt to read the data directly off the circuits themselves!!

Using an Arduino Mega as a sampling device and the tape in test mode, the team were able to read the tapes, but the header remained inscrutable and accompanied by errors in the rest of the data. Promising nonetheless!

Switching gears, the decision was made to use a logic analyzer to read the tapes and use software to decode the data. While they waited for their new analyzer to ship, one of the team members, [Jacob Filipowicz] harnessed the power of Python to write a program called Nine Track Labs (pictured below) which would allow them to read any kind of magnetic tape, at any speed, BPI, and writing standard. Armed with the software and analyzer, the team was able to successfully recover the data from the tapes in its entirety without errors!

Among the data recovered, there were numerous versions of the CROOK operating system — allowing them to reproduce the OS’s development process, as well as hundreds of other files containing programs and tools hitherto believed to be lost. There was also a backup of a ‘live’ MERA-400 system with a binary CROOK-3 OS, ready to run in emulation. All things considered, the techno-archeological tour-de-force was a smashing success.

If — in your more modern travels — you need to recover an audio recording gone awry, know that you can retrieve that data with a hex editor.