
Magnetic core memory reborn (2011) - mcbits
http://www.corememoryshield.com/report.html
======
Stratoscope
Besides being a really cool project, the article does a great job of
explaining how core memory works. Nicely done!

Here's a core memory plane I bought a few years ago. This is a 4096 bit plane
from an early-'60s Univac 418:

[https://geary.smugmug.com/Computers/History/i-jb2rgF5/A](https://geary.smugmug.com/Computers/History/i-jb2rgF5/A)

Full size close-up:

[https://geary.smugmug.com/Computers/History/i-jb2rgF5/O](https://geary.smugmug.com/Computers/History/i-jb2rgF5/O)

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GregBuchholz
People may also be interested in analog counter part: Magnetic Amplifiers.

"I had always believed that first came the vacuum tube, then the transistor,
period. But thanks to an old Navy tech manual sent in by a reader, I've
discovered a third "lost" entity. This document, unusually passionate and well
written for a military tech manual, is their promotional brochure..."

[http://teslapress.com/magamp.html](http://teslapress.com/magamp.html)

[https://archive.org/details/MagneticAmplifiers](https://archive.org/details/MagneticAmplifiers)

[https://en.wikipedia.org/wiki/Magnetic_amplifier](https://en.wikipedia.org/wiki/Magnetic_amplifier)

~~~
Aloha
There is a fourth one - the electromagnetical amplifier - essentially a
transducer mechanically coupled to a carbon microphone. While not relevant for
logic circuits, it would come at the start of that chain.

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blueintegral
I always thought it would be cool to make a necklace or something with ferrite
cores after they'd been "written" to, so you could keep a secret message with
you (albeit a short one) without suspicion.

~~~
Fjolsvith
I'm sure the TSA would be suspicious.

~~~
colejohnson66
They'd most likely make you take it off and put it through the tunnel just
because it's metal. But wouldn't that destroy the data thanks to the magnets?

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chiph
A piece of equipment I worked on in the USAF had 512 bytes of core memory. If
I recall correctly, it was constructed of nine planes of 512 cores each, where
you had 8 data planes (bits) and one parity plane. It dated from the Vietnam
war as a joint Army-Air Force project, and was being phased out in the
mid-80's with a new microprocessor-based system.

I once had to replace a defective memory assembly -- the end of messages in
the system were indicated with 4 N's in the first few columns ("NNNN") and one
of the cores went bad so the N in that column was never recognized (the other
characters in that column were munged too), and so the message never ended.
Over a day with an oscilloscope to find that one bad core and convince the
NCOIC that I was right... I didn't have a microscope, but to the naked eye the
core looked fine. It just wasn't flipping like it should have.

~~~
Fjolsvith
Was that the 490L Overseas Autovon? I went to school for that phone switch in
1987 and was in the last class before they decommissioned it for the DOD.

It had a core memory when it was initially deployed.

~~~
chiph
This was DSTE [0] connected to AUTODIN [1]. AUTOVON [2] was still around -- I
only heard of Flash Override being used once, and the recipient of the call
was sent back stateside shortly thereafter... We had a Siemens phone switch at
that base, probably because AT&Ts 5ESS wasn't available at contract-signing
time.

At a later base I was at, they were installing the then-new X.400 system [3].
It didn't last long, as SMTP ate it's lunch. Which is funny, as I got to watch
an IMP [4] get installed by the BBN [5] contractor that same year.

[0]
[http://www.1882nd.com/images/DSTE.jpg](http://www.1882nd.com/images/DSTE.jpg)

[1]
[https://en.wikipedia.org/wiki/Automatic_Digital_Network](https://en.wikipedia.org/wiki/Automatic_Digital_Network)

[2]
[https://en.wikipedia.org/wiki/Autovon](https://en.wikipedia.org/wiki/Autovon)

[3]
[https://en.wikipedia.org/wiki/Defense_Message_System](https://en.wikipedia.org/wiki/Defense_Message_System)

[4]
[https://en.wikipedia.org/wiki/Interface_Message_Processor](https://en.wikipedia.org/wiki/Interface_Message_Processor)

[5]
[https://en.wikipedia.org/wiki/BBN_Technologies](https://en.wikipedia.org/wiki/BBN_Technologies)

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blackguardx
I've always wanted to do this! Maybe I'll make the rope memory version.

[https://en.wikipedia.org/wiki/Core_rope_memory](https://en.wikipedia.org/wiki/Core_rope_memory)

~~~
walrus01
That's great how there is a measurement of 2.5MB per cubic meter. I've love to
see a 1 x 1 x 1 meter cube of rope memory... Imagine the person hours required
to do something like that, you'd have to hire professional persian carpet
weavers or something.

~~~
robryk
> Imagine the person hours required to do something like that, you'd have to
> hire professional persian carpet weavers or something.

Apollo Guidance Computer (the computer of the Apollo Command Module) has 36K
16-bit words of core rope memory. That is about 0.5MB. There were at least ten
such computers created. So, this much core rope memory was woven for the
Apollo Command Module's computers alone. See a previous discussion:

[https://news.ycombinator.com/item?id=7656282](https://news.ycombinator.com/item?id=7656282)

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ChuckMcM
That is awesome! I did a 1 bit core memory to demonstrate the principle but
this is a much better example.

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Scaevolus
Some microcontrollers have Ferroelectric RAM now-- a nonvolatile memory that's
basically magnetic core memory on a chip!

[https://en.wikipedia.org/wiki/Ferroelectric_RAM](https://en.wikipedia.org/wiki/Ferroelectric_RAM)

~~~
GregBuchholz
While it confusingly uses the "ferro" prefix, the ferroelectric effect isn't
related to magnetism.

[https://en.wikipedia.org/wiki/Ferroelectricity](https://en.wikipedia.org/wiki/Ferroelectricity)

------
dang
Previously discussed at
[https://news.ycombinator.com/item?id=3888926](https://news.ycombinator.com/item?id=3888926).

