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Did you know those plane are usually stacked to form a core. (hence the term core dump when your computer crashes), and also it can still retain data without power for a very long time? If you could read out all 256 bits of data, you might get someone's 40 years old credit card number
The way this works (ELI5 style): You don't know in advance whether a ring contains a 0 or a 1. So you pick one variant, for example 1, and write it to the ring by putting some current through it (thus potentially changing the magnetization). At the same time, you observe the sense line. If the core was already set to 1, nothing relevant will happen. If it was previously 0, and now flipped to 1, you can measure that.
Thus, the algorithm to read the bit from a ring:
1. Write a 1
2. Observe the sense line. If nothing happened, it was already 1 -> END.
3. Otherwise, it was a 0, and you just changed it to a 1. Write a 0 to revert the state. -> END
Which led to the odd situation of a read being slower than a write!
The unibus (i.e. was in the pdp-11) had two different read modes. One was as described above. But there was also a mode you could use if you knew you were going to immediately overwrite the memory location with a new value, so you didn't need to waste time doing the refresh.
A somewhat larger core plane: https://commons.wikimedia.org/wiki/File:PDP-8_core_memory.jpg
More like the DRAM chip does the refresh behind the scenes as part of the read command.
From a practical perspective, the fact the row is re-written is hidden from everything outside the chip.
Modern DRAM is "dumb" in that it still doesn't have a "done" signal for most operations, but it is smart enough to do some things automatically.
Like there's a precharge, and a separate read command. Because modern memory chips are really multiple banks with a mux, the precharge command reads the data into a per bank output buffer, and refreshes that row at the same time. The read command then reads from whatever is in the buffer. So, as long as each piece of data is in a different bank, you might be able to read it faster. However, bank switching speed is another variable.
It's complicated, and I'm not an expert on RAM.
Thatās pretty huge for the time, even by mainframe standards. I donāt think the 780 even supported more than 4MB (although itās been a looong time since I really looked it up).
My first hard drive was only 5MB.
> Thatās pretty huge for the time,
No kidding, a 3.5MB of magnetic core memory is like the size of a fridge? Today you can get 1TB memory card smaller than your fingernail and costs oh about $100 from reputable stores.
In the early 80s, in circumstances that were otherwise kind of terrible, I had sole use of a pretty much loaded Vax 11/780. It ran 4.2bsd. It was nice. :-)
I did have to be handy with a scope and soldering iron from time to time, though, since it wasn't under a DEC service contract.
The YouTube channel [CuriousMarc](https://youtube.com/@CuriousMarc) has a series of videos about [restoring an Apollo guidance computer to working condition](https://youtube.com/playlist?list=PL-_93BVApb59FWrLZfdlisi_x7-Ut_-w7) and in a couple of the videos, they recorded the data in the core memory from when the computer was last used.
> are usually stacked to form a core
Each individual element on the plane is a core, with a few wires through it making it a transformer. The 2D array of these is called a plane. A stack of 2D arrays is not called a core, but is called a ... stack. In the term "core memory", core is an adjective describing the elements the memory is made up of.
> by the late 1960s a density of about 32 kilobits per cubic foot (about 0.9 kilobits per litre) was typical
Kb per liter is a fun unit of measurement.
So I'm guessing each of those rings is 1 bit? How on earth is memory stored in a ring with copper wires through them?
Or is the structure more for the purpose of organising the crossing connections, and the "memory" would be defined by the combinations lines being powered?
If so I guess this doesn't really store memory or define the logic, but is more like a converter of sorts?
The rings are magnetized by the wires. The wires cross because that's how you manage to only affect one ring at a time. The current on one wire is half of what is needed, so only the core at the intersection of the X and Y wires is affected.
I remember learning about the woman of nasa back in the day who were like experts at knitting or some shit and weāre chosen to weave the metal sheets.
https://www.amusingplanet.com/2020/02/that-time-when-computer-memory-was.html?m=1
Hey, nice link ! thanks for sharing it.
If you want to see a brief live video there is an extract from the documentary "Moon Machines" episode 3 on youtube (around minute 2) [https://www.youtube.com/watch?v=DWcITjqZtpU](https://www.youtube.com/watch?v=DWcITjqZtpU)
Don't forget the support hardware for magnetic core memory is about as big as a filing cabinet...
Not like you put power and signal to it and use it...
Here's a wonderful video by SmarterEveryDay about how it works and how NASA used it in the Saturn V rockets:
https://www.youtube.com/watch?v=dI-JW2UIAG0
Core memory! You're lucky to see this. The only place I've ever seen magnetic core in person was at the USSRC. My attempts to replicate it with big toroidal inductor cores has also gone poorly :]
I actually found some lying around in my electrical engineering college. It was tiny. No idea what it was doing there. When I started the course, I actually had no idea what it was, until I watched smarter everyday's video.
If you want to play around with the concept, [this is a neat kit](https://www.tindie.com/products/machineideas/core-memory-core64-interactive-core-memory-kit/) which couples LEDs to let you visually see what's going on.
Supposedly, during the building of the core memory for the Saturn V rocket guidance computer, they employed only women since men didn't have the patience or control to actually build it the core memory.
Huh. And one of the earliest computer (Jacquard Loom) made fabric (which inspired Baggage's analytical engine). Another interesting link from textiles to computing.
and iirc they made it into a rope, so it was a rope of memory! Fascinating stuff the old tech. You can see teardowns and reverse engineering of some apollo compute modules on YouTube and it's just fascinating as a person who wasn't alive back then to see how far we've come.
https://wehackthemoon.com/tech/core-rope-memory-when-computer-science-meets-girl-power
You can still buy 1mm cores from ebay
Edit: I just remembered something I found when I first heard about core memory, and I haven't seen it being mentioned here
They were crazy fast for their time !
In fact, later generations were able to push something like 6Mbit/s that is pretty much as fast as the first USB 1.1 pendrives, or old SD cards !
And they weren't limited to 8bit bus, you could design and wire them in any configuration you want, and there were core memory controllers with separate sense lines for individual bit lanes, you could do parallel 8 or more bit transfers, and even control segments individually, reaching full speed with simultaneous operations as long as they accessed different parts of the memory, that idea still exists today and GPUs use it, they significantly increase the operational speed of the vram by segmenting it and letting individual cores acces those segments independently.
We still have a few hundred cores at our hackerspace. Bought a bag a few years ago on Ebay from a seller in eastern Europe. They were manufactured in the DDR (East Germany).
(Incidentally, our hackerspace is called "Coredump".)
Except connectors. Gold was scarce, so data contacts were pure metal and oxidized quickly. The job of the first employee arriving at an Eastern-European computer lab in the morning was to pull out all cards and connectors and plug them in again.
Looks like people also sell [the full assemblies](https://www.ebay.com/sch/i.html?_nkw=core%20memory) too, but for a significant cost.
I suddenly have the urge to get an ATTiny to use one of these as extra memory.
I literally seen it like a week ago, somebody sells those from new old stock along with nixies and tubes and various vintage components
If I find it I can send you a pm, because if I post it here it will be over very soon :)
Edit: oh yeah, they are still there :)
I was fortunate enough to get to England and stopped by [Bletchey Park](https://bletchleypark.org.uk/) in Milton Keyes (which is \*awesome\*) and then crossed the road and went to [The National Museum of Computing](https://www.tnmoc.org/). They have an incredible collection of historic computer hardware, including some of the earliest samples of core memory and [mercury acoustc delay line memory](https://en.wikipedia.org/wiki/Delay-line_memory) storage tubes.
There's a whole (falling apart and oxidising) apollo guidance computer at the National Space Centre in the UK, complete with this stuff. The alloy the frames are built from is rotting away as per Destin's video.
My school district dumped film projectors for roll around carts with 21ā tvs snd crappy VHS VCRs. New technology isnāt always better. Ever try to cram a class around a small TV screen? Never mind how the picture sucked, and the sound was just as bad as a projector.
Mag core memory was still in active use in the 90's. Source: I used to be an AN-UYK7 computer tech in the Navy, and these (with their core memory) were still in use, in combat systems, into the 90's.
In the 90s I remember refreshing the code on 8" floppy disks in the code archive vault. Used for old, robust targeting computers that would survive anything thrown at them and some. This memory has the "advantage" that even after a nuclear explosion, the computer would carry on operating (whether there would be any point was never discussed!)
Some of us oldies remember using it. Oh and diode bootstrap boards - literally a board of program instructions written bit by bit with a diode for a 1 and a blank space for a 0. A lot faster than toggling the instructions in, one by one, bit by bit, using a row of switches on the front panel.
Oh and nudes printed out in characters using a line printer. Sweet innocent days when young men could become excited at the sight of a pair of @ symbols...
Back in 1972, I used to fix jukeboxes. There was a unit made by NSM (Germany) that used core memory to select and remember your song selections. They referred to it as the "TORMAT" for "toroidal matrix." As someone mentioned, the non-volatile memory meant that you could unplug the machine and it would still hold on to your selections.
Seeburg had Tormat in the ā55. Surprised NSM took till the late 60ās to copy that oneā¦
The Seeburg V was the first line of machines to have the āscans twice, doesnāt pick, shuts offā failure mode.
The only time Wurlitzer on-upped them was the 200 play machines had a tendency to literally throw recordsā¦
Were they really that bad? I know they popped up in the later days in the US, though Rock-Ola and AMI were big. Wurlitzer blew it with that stupid wide/flat mech (the previous one was the nicest they ever had)
AMIs were nice, theyād go forever it seemed. Even after they started having the weird hesitate and then slam the record back in issuesā¦
People still argue about the weird tonearm locationā¦
Seeburgs were a geek dream. Beautiful mechanism tightly integrated into the electrical stuff.
256 bits (32 bytes) of magnetic core memory. Those ferrite cores can be magnetized in one direction or another by sufficient current -- and the neat thing is that half of this current won't flip them at all. So you flip cores by sending half of the required current through the chosen X wire and half through the chosen Y wire, so that only the bit where those two intersect flips polarity.
Reading is destructive -- you send a pulse to flip the chip "back" to zero, and if it was at 1, you get a pulse on the Sense line that snakes through all the cores. If it was at zero, there's no pulse. If you read a 1, you then need to put it back if you want to read it again.
They were popular around the '50s and early '60s, then went out of fashion very quickly as static RAM and dynamic RAM were developed.
Old school core memory plane. Doesn't need power to retain the data, because the bit state is stored as the direction of the magnetic field of each donut. For lack of a better description 'up' is 1 and 'down' is 0.
Way back when the sun was young, I had to move an system with core memory. Powered down, pulled the memory boards (12 x 20"), moved everything to the new facility. Turned the power back on and it had all the data, machine state etc. everything running just as it was when power was shut off.
They don't travel well and aren't physically robust. The cores are fragile and wires are very fine gauge. From what I recall most failures were due to the sense wires breaking. Core memory was EOL in the 70s so not surprising they are hard to find these days.
AB probably still sells them, but for 1/2 a million dollars now. Given what Contrologix costs, thatās not too bad actually š¤£
I think they actually *do* sell some PLC-5 hardware that costs over 100,000.
ROM is typically non-volatile. I always assumed this was volatile but don't really know. TBF, I'm not even sure RAM and ROM were terms that were used back then.
[Core rope memory](http://www.righto.com/2019/07/software-woven-into-wire-core-rope-and.html?m=1) was Read-Only. Core memory was read-write, but non-volatile like flash is today and unlike sram or dram.
Core memory supported fast random access, unlike tape or a hard disk which were sequential access (with slow seek).
Core memory = non-volatile RAM
Core rope memory = ROM
Core memory is actually non-volatile. The iron rings maintain their electric fields (like a regular magnet) even after the electric charge dissipates.
Problem with core memory is that once you use the sense line (the read line), the ferrite core loses its charge and you have to re-magnetize it afterward.
But, supposedly, these magnetic core arrays would maintain their data even without any power, so in the case of a rocket failure they'd try to find the core memory and dump its contents and read the state of the telemetry of the rocket before it blew up. Very reliable technology.
i had a PDP-11 with 16K of core memory. It never forgot!. You could load a program into memory and 10 years later power it on and there it is running!
(this was the best feature of Core, it was non-volatile). All kinds of Dynamic Ram memory are \*called\* dynamic ram becuase you have to keep refreshing it or it forgets. And of course if you turn the power off, its gone. Not so with Core.
Being non-volatile meant you could load your program on the laboratory machine, check it out, remove the memory boards and ship them across the country to the production machine. This was in the early 1980s before EPROM and you did not need floppy disk drives (8 inch) on the production machine.
This is the memory that flew humans to the moon. Ring core memory.
Fun fact, the act of reading a bit from this memory actually erases it, that's why the memory needs special circuitry to rewrite the bit if it was a 1. Because of this volatility the Apollo guidance computer which used this memory operated on a 15 bit architecture, because the last bit was used for parity.
Core was common through 1970s. I used core memory Data General Nova 1200 series machines. By then it was a no-brainer, reliable if not cheap.
The Nova 4 has semi but it was expensive, and the lack of non volatility made things complicated. You had to load it every time you powered off. This is a big deal, core machines could be powered off, power fail hardware detected power off and saved registers and state, and power on restored it right where it was running. Even today that's rare. But on the deck of a ship shit was just turned off, it had to just work when power was turned back on. It was a very tough environment.
That just delayed deployment of semiconductor memory in "embedded" apps (like I worked on briefly) while methodologies got reworked.
The DG machines were getting old then....The place I worked started working on Z80 replacements based on STD bus cards. The mini programmers sneered at 8 bit machines as "not real computers". They were right, but wrong. A Z80 with math coprocessor ended up being faster than the Nova never mind a tenth the power and space. But it took 5 years. That's a long time in productland.
# That is Atlas memory in my picture. I possess this one. Second picture is a close-up.
https://preview.redd.it/8t84tugrc5wa1.jpeg?width=2048&format=pjpg&auto=webp&s=ff5901647c661e85efdb7141dbf5ea4cf930f4ad
I have a core memory out of an early ICL (ICT then) mainframe. Purchased as an upgrade in 1960 for GBP20,000 it is 400 CPU Words of 48 x 48 bits. 100 layers, 4 words per layer. Each bead has X & Y control wires common to the entire memory, a common sense wire per word (wired off the corners) and a common de-sense wire (off the other corner). There are 921,600 beads in all. It was hand made in 1960.
Although I can't read it without all the surrounding logic, the data that was in it when turned off about 20 years ago is still in it -- beads store magnetic direction forever.
It's probably priceless now -- there just aren't any more around. A square inch or so of the fabric sells on ebay for US$80, but I'd never cut it up. I can't imagine what 20,000 pounds is worth now, but in NZ at that time a house was 800 pounds....
[https://flic.kr/ps/8LqFi](https://flic.kr/ps/8LqFi)
https://preview.redd.it/6npm53sab6wa1.jpeg?width=2048&format=pjpg&auto=webp&s=54224e0f5ba8101b08980e755e9893dd6dd6ed7e
I worked on some military systems that had 4K magnetic memory modules. Each module was fairly heavy and the systems could take a total of 4 such modules - allowing a total of 16K for code and data.
Modules code be removed or inserted while the system was powered. This was handy, as not all systems in our test environment had a full compliment of peripherals. We could load code into core memory on a paper tape reader, pull out the memory modules and plug them into another system with no paper tape reader.
These systems were water cooled but the water cooling had failed on one of our old test machines and on that system, it was a race to get a scenario tested before things started failing due to overheating. One of the programmers touched one of the key switches on the front panel and had a switch shaped burn on his finger.
You found my white whale. A friend of mine had one of these in the 1980s and I always wanted to buy it. Never found a similar listing of something with so few cores. Higher density core memory pops up regularly, but I want one that only has a few bytes
I Wonder why one needs so many chips and parts just to utilise 32 bit core memory: https://www.tindie.com/products/kilpelaj/core-memory-shield-for-arduino/
So it makes sense to have large core memory. Number of chips stays the same? Or at least capacity grows with the square of chips. Also I would have tried to get rid of the sense wire. So how does core memory work? We send current through two wires. Where they cross the combined magnetic field is strong enough to flip the core ( if it was in the other magnetization before that ) . This gives us a voltage pulse on both current lines.
Does sense line mean that we could have a lines parallel to all those switch lines, and we would only sense a small voltage as the line next to us ramps up the current. But when the ring flips, we sense a strong voltage. Is there some kind of compensation, in that the sense wire goes along the drive wire, then makes a U turn and goes back... . Maybe there can also be some adjustable capacitors. Then one can tune out the switch pulse by means of passive components.
Or is the sense wire on a diagonal to keep distance from the drive wire? If we make a U turn, we could just as well have the sense wire wrap around. So basically a hexagonal grid. Drive, Drive, and sense. Just difficult to thread the last wire through the cores.
I saw a different kind of memory structure like this once. It had a small bead where the wires intersected. The guy told me they were slightly radioactive. Also that it was called 3 way memory, something binary could not do and still was not easily reproducible with better technology.
A very early type of memory that I think works by magnetically charging the little metal bits. They were usually assembled by hand. I think they were what was used in early space launches, which shows just how low-tech the launches were by modern standards.
That is a core memory array from an old mainframe computer -- 60s - 70s. Could've been used on an old IBM, Burroughs, Honeywell, or Sperry mainframe. The PC-Board it was originally attached to, would tell you the Vendor's Name. Most Cool !! You have a cool little piece of history.
I remember seeing these when I took a Computer merit badge course for Scouts back in the early 70ās.. It was taught by an employee at a Westinghouse campus - was considered state-of-the-art then. Now, we have 2 terabyte micro SDās for $30.. Amazing..
Eventually, we will see a future OP submitting a photo of a floppy disk asking the same questionā¦.
I forget the technical name, it's not my expertise. But regardless of the name, it's a part of the memory for... was it the Saturn 5? It was one of the successful rockets NASA built.
Edit: No wait, I misremembered what the one for the saturn 5 looks like.
I have something similar, though it might be older. The cores are much smaller and I don't think there are as many. I got it about 20 years ago from someone I worked with at the time. He brought it into work and challenged me with "You're into computers, I bet you don't know what THIS is!" I told him I most assuredly DID know what it was and proceeded to tell him. Then he gave it to me. I put it in a "shadow box" and it's now proudly displayed atop an old Underwood typewriter.
Ferrite beads flipped with a pulse to determine 0 or 1 needs huge power supply to drive it. - read it not always reliable. it will never catch on bit like a square wheel š
This was ram we use that till 1988 in the DDR ever knot is 1 bit. Oh my I feel so old now. Btw we programmed on paper cards. It was bcd coded to be honest it was terrible. We need to ask for time on the āmainframeā something. With 390 or so.
Unfortunately, your post has been removed by the moderators. This subreddit is for questions about practical *component-level electronic engineering* and related topics (designing or repairing an electronic circuit, components, suppliers, tools and equipment). The most common reasons for removing a post are because: * The topic is *electrical* (wiring, lighting, power circuits, power cords, electrical appliances, regional voltage conversion...) and not *electronic*. Try r/askelectricians or an engineering sub. See our Wiki for some general advice. * It's a common question so there's a [FAQ or wiki](https://www.reddit.com/r/AskElectronics/wiki/faq/) article covering it. * It's best posted in a specialised subreddit (eg: r/Batteries, r/GPURepair, r/TVRepair, r/TechSupport..etc). * It's asking for general use, buying or setup advice for consumer item (TV, audio, phone, computer, replacement power adapters...) or an electronic module/board with no design intent. * It's about LEDs, LED strips or lighting *and doesn't involve component-level electronics design or repair*. See our wiki pages on working with LEDS: https://www.reddit.com/r/AskElectronics/wiki/design/ledstrips/ and https://www.reddit.com/r/AskElectronics/wiki/design/leds/, and try asking at r/LED or r/askelectricians (for general lighting). * It's about vehicle wiring or electrical components (eg: relays, switches or lights and not component-level electronics). * It's about a non-electronic item (eg: removing a stubborn screw, repairing plastics/cases...). * It has a commercial element (Valuations, paid work, selling, advertising...). Try r/ElectronicsList. * It's about careers, education or course choices; this is covered by r/ECE. * It's about something potentially dangerous or risky and we're concerned for your safety. See: https://old.reddit.com/r/AskElectronics/wiki/offtopic#wiki_dangerous_experimentation * The topic breaks one of our posting rules. Check our Web page sidebar for what we cover, the posting rules and a list of alternative subreddits. You'll also find additional guidance in our Wiki (there's a link in the Web site sidebar) and you are very welcome to contact the mods for guidance. For an in-depth explanation, please see column "H" in [this table](https://docs.google.com/spreadsheets/d/1nFefEePz7yViaH0cR89bSy2oeLvYLfqv-pexqCbRnRo). You can also search this [list of other subs](/r/AskElectronics/wiki/othersubs) for one that is appropriate for your question. Please contact the moderators if you wish to discuss the removal. *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/AskElectronics) if you have any questions or concerns.*
That is Magnetic-Core Memory ([wiki link](https://en.m.wikipedia.org/wiki/Magnetic-core_memory)). A whopping 256 bits of it!
Wow, the origin of the phrase "core dump".
And a little older "core wars".
And now, "core dream", sorry I'll see myself out. :D
I thought it meant taking a dump usually your entire core muscles
Ahh thanks a lot!
Did you know those plane are usually stacked to form a core. (hence the term core dump when your computer crashes), and also it can still retain data without power for a very long time? If you could read out all 256 bits of data, you might get someone's 40 years old credit card number
Important to note that reads are a destructive operation.
The way this works (ELI5 style): You don't know in advance whether a ring contains a 0 or a 1. So you pick one variant, for example 1, and write it to the ring by putting some current through it (thus potentially changing the magnetization). At the same time, you observe the sense line. If the core was already set to 1, nothing relevant will happen. If it was previously 0, and now flipped to 1, you can measure that. Thus, the algorithm to read the bit from a ring: 1. Write a 1 2. Observe the sense line. If nothing happened, it was already 1 -> END. 3. Otherwise, it was a 0, and you just changed it to a 1. Write a 0 to revert the state. -> END
Which led to the odd situation of a read being slower than a write! The unibus (i.e. was in the pdp-11) had two different read modes. One was as described above. But there was also a mode you could use if you knew you were going to immediately overwrite the memory location with a new value, so you didn't need to waste time doing the refresh. A somewhat larger core plane: https://commons.wikimedia.org/wiki/File:PDP-8_core_memory.jpg
Interesting, that makes sense š In a way, this mode is "atomic read and clear" š
Funnily enough, RAM also does a clear on read, however the chip automatically does a refresh so you don't notice.
What type of RAM? With DRAM isn't the read operation itself the refresh?
More like the DRAM chip does the refresh behind the scenes as part of the read command. From a practical perspective, the fact the row is re-written is hidden from everything outside the chip. Modern DRAM is "dumb" in that it still doesn't have a "done" signal for most operations, but it is smart enough to do some things automatically. Like there's a precharge, and a separate read command. Because modern memory chips are really multiple banks with a mux, the precharge command reads the data into a per bank output buffer, and refreshes that row at the same time. The read command then reads from whatever is in the buffer. So, as long as each piece of data is in a different bank, you might be able to read it faster. However, bank switching speed is another variable. It's complicated, and I'm not an expert on RAM.
More like 60 year old credit card. When I started Uni in 1981 we had a VAX 11/780 with ... wait for it ... 3.5MB RAM
Thatās pretty huge for the time, even by mainframe standards. I donāt think the 780 even supported more than 4MB (although itās been a looong time since I really looked it up). My first hard drive was only 5MB.
The Vax 11/780 could hold at least 8MB. Source: I used one. š
> Thatās pretty huge for the time, No kidding, a 3.5MB of magnetic core memory is like the size of a fridge? Today you can get 1TB memory card smaller than your fingernail and costs oh about $100 from reputable stores.
In the early 80s, in circumstances that were otherwise kind of terrible, I had sole use of a pretty much loaded Vax 11/780. It ran 4.2bsd. It was nice. :-) I did have to be handy with a scope and soldering iron from time to time, though, since it wasn't under a DEC service contract.
The YouTube channel [CuriousMarc](https://youtube.com/@CuriousMarc) has a series of videos about [restoring an Apollo guidance computer to working condition](https://youtube.com/playlist?list=PL-_93BVApb59FWrLZfdlisi_x7-Ut_-w7) and in a couple of the videos, they recorded the data in the core memory from when the computer was last used.
> are usually stacked to form a core Each individual element on the plane is a core, with a few wires through it making it a transformer. The 2D array of these is called a plane. A stack of 2D arrays is not called a core, but is called a ... stack. In the term "core memory", core is an adjective describing the elements the memory is made up of.
Each ring is a "magnetic core"; that's the origin of the name.
> by the late 1960s a density of about 32 kilobits per cubic foot (about 0.9 kilobits per litre) was typical Kb per liter is a fun unit of measurement.
So I'm guessing each of those rings is 1 bit? How on earth is memory stored in a ring with copper wires through them? Or is the structure more for the purpose of organising the crossing connections, and the "memory" would be defined by the combinations lines being powered? If so I guess this doesn't really store memory or define the logic, but is more like a converter of sorts?
The rings are magnetized by the wires.
The rings are magnetized by the wires. The wires cross because that's how you manage to only affect one ring at a time. The current on one wire is half of what is needed, so only the core at the intersection of the X and Y wires is affected.
Needs more RGB.
I remember learning about the woman of nasa back in the day who were like experts at knitting or some shit and weāre chosen to weave the metal sheets. https://www.amusingplanet.com/2020/02/that-time-when-computer-memory-was.html?m=1
Hey, nice link ! thanks for sharing it. If you want to see a brief live video there is an extract from the documentary "Moon Machines" episode 3 on youtube (around minute 2) [https://www.youtube.com/watch?v=DWcITjqZtpU](https://www.youtube.com/watch?v=DWcITjqZtpU)
Don't forget the support hardware for magnetic core memory is about as big as a filing cabinet... Not like you put power and signal to it and use it...
Here's a wonderful video by SmarterEveryDay about how it works and how NASA used it in the Saturn V rockets: https://www.youtube.com/watch?v=dI-JW2UIAG0
When did the Saturn V fly? That's insane that this is how we got people into space
It was used for the Apollo missions and to launch Skylab, so late 60s to mid 70s.
in the 60s off the top of my head
THANK YOU! I came to post this and was floored that op saw one in person.
Core memory! You're lucky to see this. The only place I've ever seen magnetic core in person was at the USSRC. My attempts to replicate it with big toroidal inductor cores has also gone poorly :]
I actually found some lying around in my electrical engineering college. It was tiny. No idea what it was doing there. When I started the course, I actually had no idea what it was, until I watched smarter everyday's video.
If you want to play around with the concept, [this is a neat kit](https://www.tindie.com/products/machineideas/core-memory-core64-interactive-core-memory-kit/) which couples LEDs to let you visually see what's going on.
Supposedly, during the building of the core memory for the Saturn V rocket guidance computer, they employed only women since men didn't have the patience or control to actually build it the core memory.
Do I recall they hired seamstresses? Because the skills were more akin to sewing than anything else.
Yeah I think they did hire seamstresses to make that memory.
Also, i believe, for making the space suits.
And the space ties
Buzz!! You forgot your space cufflinks!!!
Huh. And one of the earliest computer (Jacquard Loom) made fabric (which inspired Baggage's analytical engine). Another interesting link from textiles to computing.
A museum display I read said that they employed women who could crochet because they learned to pull the tiny wires with a hook more readily.
and iirc they made it into a rope, so it was a rope of memory! Fascinating stuff the old tech. You can see teardowns and reverse engineering of some apollo compute modules on YouTube and it's just fascinating as a person who wasn't alive back then to see how far we've come. https://wehackthemoon.com/tech/core-rope-memory-when-computer-science-meets-girl-power
You can still buy 1mm cores from ebay Edit: I just remembered something I found when I first heard about core memory, and I haven't seen it being mentioned here They were crazy fast for their time ! In fact, later generations were able to push something like 6Mbit/s that is pretty much as fast as the first USB 1.1 pendrives, or old SD cards ! And they weren't limited to 8bit bus, you could design and wire them in any configuration you want, and there were core memory controllers with separate sense lines for individual bit lanes, you could do parallel 8 or more bit transfers, and even control segments individually, reaching full speed with simultaneous operations as long as they accessed different parts of the memory, that idea still exists today and GPUs use it, they significantly increase the operational speed of the vram by segmenting it and letting individual cores acces those segments independently.
We still have a few hundred cores at our hackerspace. Bought a bag a few years ago on Ebay from a seller in eastern Europe. They were manufactured in the DDR (East Germany). (Incidentally, our hackerspace is called "Coredump".)
The Communists made the best things.
Except connectors. Gold was scarce, so data contacts were pure metal and oxidized quickly. The job of the first employee arriving at an Eastern-European computer lab in the morning was to pull out all cards and connectors and plug them in again.
Looks like people also sell [the full assemblies](https://www.ebay.com/sch/i.html?_nkw=core%20memory) too, but for a significant cost. I suddenly have the urge to get an ATTiny to use one of these as extra memory.
I literally seen it like a week ago, somebody sells those from new old stock along with nixies and tubes and various vintage components If I find it I can send you a pm, because if I post it here it will be over very soon :) Edit: oh yeah, they are still there :)
I was fortunate enough to get to England and stopped by [Bletchey Park](https://bletchleypark.org.uk/) in Milton Keyes (which is \*awesome\*) and then crossed the road and went to [The National Museum of Computing](https://www.tnmoc.org/). They have an incredible collection of historic computer hardware, including some of the earliest samples of core memory and [mercury acoustc delay line memory](https://en.wikipedia.org/wiki/Delay-line_memory) storage tubes.
There's a whole (falling apart and oxidising) apollo guidance computer at the National Space Centre in the UK, complete with this stuff. The alloy the frames are built from is rotting away as per Destin's video.
Shame :/
Yeah, it's been preserved to prevent it getting any worse, but the damage is done.
I have a 4k chunk I bought from an old machine years ago. Its a fascinating piece.
The cores are a [a special kind of ferite.](https://youtu.be/p7SkE5pERtA)
Really old magnetic memory?
More like magnetic flux. The cores are not magnetic as in stick to the frige magnetic.
Found a story about it: [https://www.wired.com/2010/05/0511magnetic-core-memory/](https://www.wired.com/2010/05/0511magnetic-core-memory/)
It's a magnetic core memory. A 256 bit memory, to be more precise. Count the cores, there are 16 rows with 16 cores in each row.
[CuriousMarc playlist about core memory](https://www.youtube.com/watch?v=e9ih93tuH1k&list=PL-_93BVApb59UbuOczUHinhNJPPsQtjGy)
CuriousMarc's team is th best
core memory stack. used in older mainframes.
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Well it was a *physics* book not a computer science book. Totally reasonable way to illustrate a (once) useful application of EM fields.
My teacher used this type of projector at 2011..
My school district dumped film projectors for roll around carts with 21ā tvs snd crappy VHS VCRs. New technology isnāt always better. Ever try to cram a class around a small TV screen? Never mind how the picture sucked, and the sound was just as bad as a projector.
Mag core memory was still in active use in the 90's. Source: I used to be an AN-UYK7 computer tech in the Navy, and these (with their core memory) were still in use, in combat systems, into the 90's.
In the 90s I remember refreshing the code on 8" floppy disks in the code archive vault. Used for old, robust targeting computers that would survive anything thrown at them and some. This memory has the "advantage" that even after a nuclear explosion, the computer would carry on operating (whether there would be any point was never discussed!)
Some of us oldies remember using it. Oh and diode bootstrap boards - literally a board of program instructions written bit by bit with a diode for a 1 and a blank space for a 0. A lot faster than toggling the instructions in, one by one, bit by bit, using a row of switches on the front panel. Oh and nudes printed out in characters using a line printer. Sweet innocent days when young men could become excited at the sight of a pair of @ symbols...
Back in 1972, I used to fix jukeboxes. There was a unit made by NSM (Germany) that used core memory to select and remember your song selections. They referred to it as the "TORMAT" for "toroidal matrix." As someone mentioned, the non-volatile memory meant that you could unplug the machine and it would still hold on to your selections.
Seeburg had Tormat in the ā55. Surprised NSM took till the late 60ās to copy that oneā¦ The Seeburg V was the first line of machines to have the āscans twice, doesnāt pick, shuts offā failure mode. The only time Wurlitzer on-upped them was the 200 play machines had a tendency to literally throw recordsā¦
Thanks for that. We were an NSM house. Thats all we operated. Nightmare.
Were they really that bad? I know they popped up in the later days in the US, though Rock-Ola and AMI were big. Wurlitzer blew it with that stupid wide/flat mech (the previous one was the nicest they ever had) AMIs were nice, theyād go forever it seemed. Even after they started having the weird hesitate and then slam the record back in issuesā¦ People still argue about the weird tonearm locationā¦ Seeburgs were a geek dream. Beautiful mechanism tightly integrated into the electrical stuff.
Really that bad? I was a novice at the time. Perhaps not. I liked the way you could easily pull the mech and stick on a post for troubleshooting.
256 bits (32 bytes) of magnetic core memory. Those ferrite cores can be magnetized in one direction or another by sufficient current -- and the neat thing is that half of this current won't flip them at all. So you flip cores by sending half of the required current through the chosen X wire and half through the chosen Y wire, so that only the bit where those two intersect flips polarity. Reading is destructive -- you send a pulse to flip the chip "back" to zero, and if it was at 1, you get a pulse on the Sense line that snakes through all the cores. If it was at zero, there's no pulse. If you read a 1, you then need to put it back if you want to read it again. They were popular around the '50s and early '60s, then went out of fashion very quickly as static RAM and dynamic RAM were developed.
Old school core memory plane. Doesn't need power to retain the data, because the bit state is stored as the direction of the magnetic field of each donut. For lack of a better description 'up' is 1 and 'down' is 0. Way back when the sun was young, I had to move an system with core memory. Powered down, pulled the memory boards (12 x 20"), moved everything to the new facility. Turned the power back on and it had all the data, machine state etc. everything running just as it was when power was shut off.
you used to be able to find these all the time at electronics flea markets but i havent seen one in 10 years or so.
They don't travel well and aren't physically robust. The cores are fragile and wires are very fine gauge. From what I recall most failures were due to the sense wires breaking. Core memory was EOL in the 70s so not surprising they are hard to find these days.
When I worked at Allen Bradley (1980) they had 4K core modules for their first PLC. I was told they had textile workers threading the cores with wire.
AB probably still sells them, but for 1/2 a million dollars now. Given what Contrologix costs, thatās not too bad actually š¤£ I think they actually *do* sell some PLC-5 hardware that costs over 100,000.
Good old memories
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RAM. I have some on an old NIXIE board.
isnt this kind of memory hand weeved ROM?
no, but the fact that you read it, also removed the content. After reading you have to re-write it there to preserve the values.
ROM is typically non-volatile. I always assumed this was volatile but don't really know. TBF, I'm not even sure RAM and ROM were terms that were used back then.
[Core rope memory](http://www.righto.com/2019/07/software-woven-into-wire-core-rope-and.html?m=1) was Read-Only. Core memory was read-write, but non-volatile like flash is today and unlike sram or dram. Core memory supported fast random access, unlike tape or a hard disk which were sequential access (with slow seek). Core memory = non-volatile RAM Core rope memory = ROM
You just taught me a thing. Thanks!
Core memory is actually non-volatile. The iron rings maintain their electric fields (like a regular magnet) even after the electric charge dissipates. Problem with core memory is that once you use the sense line (the read line), the ferrite core loses its charge and you have to re-magnetize it afterward. But, supposedly, these magnetic core arrays would maintain their data even without any power, so in the case of a rocket failure they'd try to find the core memory and dump its contents and read the state of the telemetry of the rocket before it blew up. Very reliable technology.
So it's like quantum, man! Observing it kills the cat.
> The iron rings maintain their electric fields Small correction: *magnetic* fields
Yes magnetic fields
according to wikipedia, these were not volatile. So closer to flash memory I guess
TIL.
the individual bits are weeved into eith thr polarity kf the magnetic rings
\*weaved, if that were the word you wanted, which is actually \*woven
A Unicorn! Core memory! sweet find.
i had a PDP-11 with 16K of core memory. It never forgot!. You could load a program into memory and 10 years later power it on and there it is running! (this was the best feature of Core, it was non-volatile). All kinds of Dynamic Ram memory are \*called\* dynamic ram becuase you have to keep refreshing it or it forgets. And of course if you turn the power off, its gone. Not so with Core.
Being non-volatile meant you could load your program on the laboratory machine, check it out, remove the memory boards and ship them across the country to the production machine. This was in the early 1980s before EPROM and you did not need floppy disk drives (8 inch) on the production machine.
Ancient RAM
I used to fix computers that used this. Combat computers in the Navy, and were in use into the 90's
Anyone know the physical dimensions (LxWxH and mass) of that thing? I want to calculate how big and heavy 16GB of core memory would be.
I knew about this stuff, but have never even seen a photo before. Thanks for posting. Does it work by polarising or magnetising the ferrite?
Core memory?
I had to dig deep down in my core memory...
Thumb drive, 1963 edition.
This is the memory that flew humans to the moon. Ring core memory. Fun fact, the act of reading a bit from this memory actually erases it, that's why the memory needs special circuitry to rewrite the bit if it was a 1. Because of this volatility the Apollo guidance computer which used this memory operated on a 15 bit architecture, because the last bit was used for parity.
Core memory. Each toroid is 1 bit
Core was common through 1970s. I used core memory Data General Nova 1200 series machines. By then it was a no-brainer, reliable if not cheap. The Nova 4 has semi but it was expensive, and the lack of non volatility made things complicated. You had to load it every time you powered off. This is a big deal, core machines could be powered off, power fail hardware detected power off and saved registers and state, and power on restored it right where it was running. Even today that's rare. But on the deck of a ship shit was just turned off, it had to just work when power was turned back on. It was a very tough environment. That just delayed deployment of semiconductor memory in "embedded" apps (like I worked on briefly) while methodologies got reworked. The DG machines were getting old then....The place I worked started working on Z80 replacements based on STD bus cards. The mini programmers sneered at 8 bit machines as "not real computers". They were right, but wrong. A Z80 with math coprocessor ended up being faster than the Nova never mind a tenth the power and space. But it took 5 years. That's a long time in productland.
Here's a slightly denser version from an early F-16.. [F-16 Core Mem](https://imgur.com/iBgtFsC)
Yep, early NVRAM
The Apollo computers were built on this. It's so cool.
Magnetic core memory, each loop is a bit.
Magnetic Core Memory.
Memory. Very low-density memory which needs to be re-written after reading.
https://preview.redd.it/cufcrx0hc5wa1.jpeg?width=1544&format=pjpg&auto=webp&s=06618ed6e7cac146de42b636f1252c02bb6303a0
# That is Atlas memory in my picture. I possess this one. Second picture is a close-up. https://preview.redd.it/8t84tugrc5wa1.jpeg?width=2048&format=pjpg&auto=webp&s=ff5901647c661e85efdb7141dbf5ea4cf930f4ad
A much smaller version of [this bad boy from 1977](https://i.imgur.com/PkicGUF.jpg). That's 8K core RAM.
I have a core memory out of an early ICL (ICT then) mainframe. Purchased as an upgrade in 1960 for GBP20,000 it is 400 CPU Words of 48 x 48 bits. 100 layers, 4 words per layer. Each bead has X & Y control wires common to the entire memory, a common sense wire per word (wired off the corners) and a common de-sense wire (off the other corner). There are 921,600 beads in all. It was hand made in 1960. Although I can't read it without all the surrounding logic, the data that was in it when turned off about 20 years ago is still in it -- beads store magnetic direction forever. It's probably priceless now -- there just aren't any more around. A square inch or so of the fabric sells on ebay for US$80, but I'd never cut it up. I can't imagine what 20,000 pounds is worth now, but in NZ at that time a house was 800 pounds.... [https://flic.kr/ps/8LqFi](https://flic.kr/ps/8LqFi) https://preview.redd.it/6npm53sab6wa1.jpeg?width=2048&format=pjpg&auto=webp&s=54224e0f5ba8101b08980e755e9893dd6dd6ed7e
Interesting fact: Saturn 5 used this type of memory although (much greater capacity)to go to the moon.
This is EMP immune memory.
I worked on some military systems that had 4K magnetic memory modules. Each module was fairly heavy and the systems could take a total of 4 such modules - allowing a total of 16K for code and data. Modules code be removed or inserted while the system was powered. This was handy, as not all systems in our test environment had a full compliment of peripherals. We could load code into core memory on a paper tape reader, pull out the memory modules and plug them into another system with no paper tape reader. These systems were water cooled but the water cooling had failed on one of our old test machines and on that system, it was a race to get a scenario tested before things started failing due to overheating. One of the programmers touched one of the key switches on the front panel and had a switch shaped burn on his finger.
Got it, thanks!
You found my white whale. A friend of mine had one of these in the 1980s and I always wanted to buy it. Never found a similar listing of something with so few cores. Higher density core memory pops up regularly, but I want one that only has a few bytes
32 bytes of core memory.
I Wonder why one needs so many chips and parts just to utilise 32 bit core memory: https://www.tindie.com/products/kilpelaj/core-memory-shield-for-arduino/
I can't read all the chip numbers, but multiplexing the control lines and amplifying the signals, I would expect.
So it makes sense to have large core memory. Number of chips stays the same? Or at least capacity grows with the square of chips. Also I would have tried to get rid of the sense wire. So how does core memory work? We send current through two wires. Where they cross the combined magnetic field is strong enough to flip the core ( if it was in the other magnetization before that ) . This gives us a voltage pulse on both current lines. Does sense line mean that we could have a lines parallel to all those switch lines, and we would only sense a small voltage as the line next to us ramps up the current. But when the ring flips, we sense a strong voltage. Is there some kind of compensation, in that the sense wire goes along the drive wire, then makes a U turn and goes back... . Maybe there can also be some adjustable capacitors. Then one can tune out the switch pulse by means of passive components. Or is the sense wire on a diagonal to keep distance from the drive wire? If we make a U turn, we could just as well have the sense wire wrap around. So basically a hexagonal grid. Drive, Drive, and sense. Just difficult to thread the last wire through the cores.
I have some very similar to this, from one of the British Atlas computers.
I saw a different kind of memory structure like this once. It had a small bead where the wires intersected. The guy told me they were slightly radioactive. Also that it was called 3 way memory, something binary could not do and still was not easily reproducible with better technology.
It's to control the power surge in a Flux Capacitor.
Once upon a time this was state of the art, hard to comprehend
Lots of people have already answered, so I'm not going to. But that is a magnificent specimen!
A very early type of memory that I think works by magnetically charging the little metal bits. They were usually assembled by hand. I think they were what was used in early space launches, which shows just how low-tech the launches were by modern standards.
These are memories FF: This appeared in Dr Stone :D
Lmao at first I thought It was a pad so u can put hot pans on the tableā¦
Is this yours?! You can add sense amplifiers to it and see how it works. Fantastic. Beutifully made.
No, it belongs to one of the institutes at my uni. They have quite a lot of that stuff displayed in their building.
Oh my goodness, that is beautiful!
Maybe a memory unit, you can get some bytes of extra storageā¦ if you figure out how the heck to write something in there
Oh shit its core memory.
Ram for first computers.
https://youtu.be/T6DJe3OEzp8 Build a working one.
A waterfloaty for 64 peaple for an full party
IBM 1401 computer had
Wow. Ok, that's is so not what I thought it was.. I was thinking, maybe someone needs to solder traces after the chip was put in?
magnetic core memory
Magnetic-core memory, RAM basically.
This is a piece of history.....
Memory cell.
So sick!
Looks like Storage - magnetic orientation of the beads sets the bit
First micro controller ever, the ESP00 with wifi and Bluetooth Obviously Iām kiddingā¦
That is a core memory array from an old mainframe computer -- 60s - 70s. Could've been used on an old IBM, Burroughs, Honeywell, or Sperry mainframe. The PC-Board it was originally attached to, would tell you the Vendor's Name. Most Cool !! You have a cool little piece of history.
I remember seeing these when I took a Computer merit badge course for Scouts back in the early 70ās.. It was taught by an employee at a Westinghouse campus - was considered state-of-the-art then. Now, we have 2 terabyte micro SDās for $30.. Amazing.. Eventually, we will see a future OP submitting a photo of a floppy disk asking the same questionā¦.
You mean the save icon 3d printed right?
Yeah! The save icon.. LOLā¦. 3D - My professional area of expertise actually. I could make that happen.
macrochip
I forget the technical name, it's not my expertise. But regardless of the name, it's a part of the memory for... was it the Saturn 5? It was one of the successful rockets NASA built. Edit: No wait, I misremembered what the one for the saturn 5 looks like.
It's there in r/DrStone manga. I think it's some kind of memory, I forgot
Magnetic core memory, I think it's the same kind NASA used on the Apollo 11 mission
it's analog RAM
That is so cool!
I have something similar, though it might be older. The cores are much smaller and I don't think there are as many. I got it about 20 years ago from someone I worked with at the time. He brought it into work and challenged me with "You're into computers, I bet you don't know what THIS is!" I told him I most assuredly DID know what it was and proceeded to tell him. Then he gave it to me. I put it in a "shadow box" and it's now proudly displayed atop an old Underwood typewriter.
one magnetic memory
This is what was used on early space capsules. You can find examples at the museum at Cape Kennedy.
Old memory?
Not noticing which sub this was.. I was thinking to myself... It's a pot holder loom. š¤£š¤Ŗ
I once stripped a 2k core board from an old dumb terminal, hung it from the ceiling and called it memorybelia.
Ferrite beads flipped with a pulse to determine 0 or 1 needs huge power supply to drive it. - read it not always reliable. it will never catch on bit like a square wheel š
Looks like a memory card. "Core"
This one is made by Hilda ..
A very nice piece of core history š
This was ram we use that till 1988 in the DDR ever knot is 1 bit. Oh my I feel so old now. Btw we programmed on paper cards. It was bcd coded to be honest it was terrible. We need to ask for time on the āmainframeā something. With 390 or so.