Saving Apollo By Decoding Core Rope

One of our favorite retro hardware enthusiasts, [CuriousMarc], is back with the outstanding tale of preserving Apollo Program software, and building a core rope reader from scratch to do it. We’ve talked about [Marc]’s previous efforts to get real Apollo hardware working again, and one of the by-products of this effort was recovering the contents of the read-only core rope memory modules that were part of that hardware.

The time finally came to hand the now-working Apollo guidance computer back to its owner, which left the team without any hardware to read core rope modules. But the archive of software from the program was still incomplete, and there were more modules to try to recover. So, the wizardly [Mike Stewart] just decided to roll up his sleeves and build his own reader. Which didn’t actually work as expected the first time.

And this leads us into one of [Marc]’s elevator music explainers, where he gives a beautiful rundown on how core rope works. And if you are thinking of core memory based on ferrite cores, get ready for a brain stretch, as core rope is quite a bit different, and is even more complicated to read. Which brings us to the bug in [Mike]’s reader, which is actually a bug in the block II design of the core rope modules.

Reading a byte off the module requires setting multiple inhibit wires to select an individual core. An innovation in block II allowed those inhibit wires to run at half current, but it turns out that didn’t actually work as intended, and partially selected multiple cores on the other half of the module. And [Mike] forget to re-implement that bug — the reader needs to literally be bug-for-bug compatible. A quick recompile of the FPGA code makes everything work again. And the conservation effort can continue. Stay tuned for more in the Apollo story!

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GLASNOST Is A Computer That Makes Transparency A Priority

We live in a world where most of us take the transistor for granted. Within arm’s length of most people reading this, there are likely over ten billion of them sending electrons in every direction. But the transistor was not the first technology to come around to make the computer a possibility, but if you go to the lengths of building something with an alternative, like this vacuum tube computer, you may appreciate them just a tiny bit more.

This vacuum tube computer is called GLASNOST, which according to its creator [Paul] means “glass, no semiconductors” with the idea that the working parts of the computer (besides the passive components) are transparent glass tubes, unlike their opaque silicon-based alternatives. It boasts a graphical display on an oscilloscope, 4096 words of memory, and a custom four-bit architecture based only on NOT, NOR, and OR gates which are simpler to create with the bulky tubes.

The project is still a work in progress but already [Paul] has the core memory figured out and the computer modeled in a logic simulator. The next steps are currently being worked through which includes getting the logic gates to function in the real world. We eagerly await the next steps of this novel computer and, if you want to see one that was built recently and not in the distant past of the 1950s, take a look at the Electron Tube New Automatic Computer that was completed just a few years ago.

Supercon 2022: Andy Geppert Is Bringing Core Memory Back

Many Hackaday readers will be familiar with the term “core memory”, likely thanks to its close association with the Apollo Guidance Computer. But knowing that the technology existed at one point and actually understanding how it worked is another thing entirely. It’s a bit like electronic equivalent to the butter churn — you’ve heard of it, you could probably even identify an image of one — but should somebody hand you one and ask you to operate it, the result probably won’t be too appetizing.

That’s where Andy Geppert comes in. He’s turned his own personal interest into magnetic core memory into a quest to introduce this fascinating technology to a whole new generation thanks to some modern enhancements through his Core64 project. By mating the antiquated storage technology with a modern microcontroller and LEDs, it’s transformed into an interactive visual experience. Against all odds, he’s managed to turned a technology that helped put boots on the Moon half a century ago into a gadget that fascinates both young and old.

In this talk at the 2022 Hackaday Supercon, Andy first talks the audience through the basics of magnetic core memory as it was originally implemented. From there, he explains the chain of events that lead to the development of the Core64 project, and talks a bit about where he hopes it can go in the future.

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VCF East 2023: Andy Geppert Talks Core Memory

Do you know core memory? Our prehistoric predecessors would store data in the magnetic fields of ferrite rings, reading out the ones and zeroes by setting the magnetic field and detecting if a small current is induced in a sense wire, indicating that the bit flipped, or not detecting the current, in which case it didn’t. Core memory is non-volatile, rad hard, and involved a tremendous amount of wire weaving to fabricate. And it’s pretty cool.

[Andy Geppert] wants to get you hands-on with this anachronistic memory, and builds kits to demo how it works. [Tom Nardi] and [Bil Herd] caught up with him at the Vintage Computer Festival East last weekend, and got him to demo his Core64 project for them. (Video, embedded below.)

The design of Core64 displays its state in lights at all times. And this means that you can write to it using either the onboard Pi Pico, for a blinky light show, or with a magnetic stylus, setting each bit’s magnetic state by hand. This turns it into a magnetic memory tablet and is a sweet demonstration of the principles that make it all work. Or, if you pulse the lines at just the right frequency, you can make the cores spin!

Watch [Andy] explaining it in our interview here, and stay tuned for more coming from VCF East 2023 soon.

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Soviet-Era Auto Dialler Uses Magnetic Rope Core Memory

We’ve seen a few interesting magnetic core memories on these fine pages over the years, but we don’t recall seeing too many user programmable magnetic core memory devices. This interesting Russian telephone auto dialer in its day would have been a very useful device, capable of storing and dialing forty user programmable 7-digit numbers. [mikeselectricstuff] tore into one (video, embedded below), and found some very interesting tech. For its era, this is high technology stuff. Older Russian tech has a reputation for incredibly ingenious use of older parts, that can’t be denied. After all, if it works, then there’s no need to change it. But anyway, what’s interesting here is how the designers decided to solve the problem of programming and recalling of numbers, without using a microprocessor, by using discrete logic and core rope memory.

This is the same technology used by the Apollo Guidance Computer, but in a user configurable form, and obviously much smaller storage capacity. The core array consists of seven, four-bit words, one word per telephone digit, which will be read out sequentially bottom to top. The way you program your number is to take your programming wire, insert it into the appropriate hole (one row related to numbers 1-20, the other row is shifted 1-20 for the second bank) and thread it along the cores in a weave type pattern. Along the way, the wire is passed through or bypasses a particular core, depending upon the digit you are coding for. They key for this encoding is written on the device’s lid. At the end, you then need to terminate the wire in the matching top connector, to allow the circuit to be completed.

As far as we can tell, the encoding is a binary sequence, with a special ‘stop’ code to indicate telephone numbers with less than seven digits. We shall leave further analysis to interested parties, and just point you at the Original manufacturer schematics. Enjoy!

Of course we’re not just going to mention rope core memory and the AGC without linking to a fantastic article about the very same, and if that’s wetting your appetite for making a rope core memory, here’s a little thing about that too!

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Taking A Walk Down [Computer] Memory Lane

There’s nothing quite like going to a museum and being given a tour by a docent who really knows their way around the exhibits. When that docent has first hand experience in the subject matter, the experience is enhanced even further. So you can imagine our excitement when hacker, maker, and former DEC mainframe memory engineer [Ned Utzig] published a tour of what he calls “Memories of Weird Memories of Computers Past.” [Ned] expertly guides us through each technology, adding flavor and nuance to an already fascinating subject.

The tour begins with early storage media such as IBM punch cards, and then walks us through time to the paper tape, vacuum tubes, and even complex vats of mercury — all used for the sake of storing data either permanently or temporarily.

Next in the exhibit is an impressive CRT hack that isn’t unlike modern DRAM. The tour continues on to ferrite core memory such as that used on mainframes, minicomputers, and even the Apollo Guidance Computer. Each type is examined for its strengths and weaknesses and its place in computing history.

We really appreciated the imaginative question posed toward the end of the article. We won’t give it away here- it’s worth it to go give The Mad Ned Memo a read.

Is obsolete technology your cup of tea? Perhaps an Arduino based experiment with core memory will scratch the itch, or maybe storing data in thin air will bring back memories of computers gone by.

Visualizing Magnetic Memory With Core 64

For the vast majority of us, computer memory is a somewhat abstract idea. Whether you’re declaring a variable in Python or setting a register in Verilog, the data goes — somewhere — and the rest really isn’t your problem. You may have deliberately chosen the exact address to write to, but its not like you can glance at a stick of RAM and see the data. And you almost certainly can’t rewrite it by hand. (If you can do either of those things, let us know.)

These limitations must have bothered [Andy Geppert], because he set out to bring computer memory into the tangible (or at least, visible) world with his interactive memory badge Core 64. [Andy] has gone through a few different iterations, but essentially Core 64 is an 8×8 grid of woven core memory, which stores each bit via magnetic polarization, with a field of LEDs behind it that allow you to visualize what’s stored. The real beauty of this setup is that it it can be used to display 64 pixel graphics. Better yet — a bit can be rewritten by introducing a magnetic field at the wire junction. In other words, throw a magnet on a stick into the mix and you have yourself a tiny drawing tablet!

This isn’t the first time we’ve seen cool experiments with core memory, and not even the first time we’ve seen [Andy] use it to make something awesome, but it really illuminates how the technology works. Being able to not only see memory being written but to manually write to it makes it all so much realer, somehow.

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