core memory

19 Articles

A Nibble Of Core Memory, In An SAO

September 3, 2024 by 15 Comments

Core memory, magnetized memory using tiny magnetic rings suspended on a grid of wires, is now more than five decades obsolete, yet it exerts a fascination for hardware hackers still. Not least [Andy Geppert], who’s made a nibble, four bits of it, complete with interactive LED illumination to show state. Best of all, it’s on a badge Simple Add-On (SAO) for fun and games at your next hacker con.

Aside from it being a fun project, perhaps the most interesting part comes in the GitHub repository, where can be found the schematic for the device. He’s built all the drive and sense circuitry himself rather than finding an old-stock core memory driver chip, which gives those of us who’ve never worked with this stuff the chance to understand how it works. Beyond that it takes input from the Stemma or SAO ports to a GPIO expander, which provides all the lines necessary to drive it all.

To show it in action he’s posted a video which we’ve placed below. If you’re hungry for more, it’s not [Andy]’s first outing into core memory.

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Inside A Mystery Aerospace Computer With [Ken Shirriff]

June 1, 2024 by 10 Comments

When life hands you a mysterious bit of vintage avionics, your best bet to identifying it might just be to get it in front of the biggest bunch of hardware hounds on the planet. After doing a teardown and some of your own investigation first, of course.

The literal black box in question came into [Ken Shirriff]’s custody courtesy of [David] from Usagi Electric, better known for his vacuum tube computer builds and his loving restoration of a Centurion minicomputer. The unit bears little in the way of identifying markings, but [Ken] was able to glean a little by inspecting the exterior. The keypad is a big giveaway; its chunky buttons seem optimized for use with the gloved hands of a pressure suit, and the ordinal compass points hint at a navigational function. The layout of the keypad is similar to the Apollo DSKY, which might make it a NASA artifact. Possibly contradicting all of that is the oddball but very cool electromechanical display, which uses reels of digits and a stepper-like motor to drive them.

Inside, more mysteries — and more clues — await. Unlike a recent flight computer [Ken] looked at, most of the guts are strictly electronic. The instrument is absolutely stuffed with PCBs, most of which are four-layer boards. Date codes on the hundreds of chips all seem to be in the 1967 range, dating the unit to the late 60s or early 70s. The weirdest bit is the core memory buried deep inside the stacks of logic and analog boards. [Ken] found 20 planes with the core, hinting at a 20-bit processor.

In the end, [Ken] was unable to come to any firm conclusion as to what this thing is, who made it, or what its purpose was. We doubt that his analysis will end there, though, and we look forward to the reverse engineering effort on this piece of retro magic.

What’s A Transfluxor?

March 3, 2024 by 11 Comments

In the 1967 movie The Graduate, a wise older man gives some advice to the title character: plastics. Indeed, plastics would become big business. In 1962, though, a computer-savvy character might have offered a different word: transfluxor. What’s a transfluxor? Well, according to computer history sleuth [Ken Shirriff], it was the heart of a 20-pound transistor computer from Arma. Of course, plastics turned out to be a better bet, but in 1962, the transfluxor seemed to be the wave of the future.

In 1962, most computers were room-sized, but the Arma was “micro” taking up just 0.4 cubic feet — less than an Apple II. It would eventually spawn computers used in ships at sea and airplanes ranging from the Concorde to Air Force One.

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Saving Apollo By Decoding Core Rope

November 4, 2023 by 7 Comments

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

July 17, 2023 by 7 Comments

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

May 18, 2023 by 22 Comments

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

April 20, 2023 by 18 Comments

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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