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One Bit Ferrite Core Memory

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Our hackerspace name https://coredump.ch and logo are based on core memory :)

We still want to build an 8x8 (or maybe just 8x7) bit core memory one day to be able to store the word "coredump" as ASCII in it.

Some time ago we bought some cores on ebay and did setup a 2x2 matrix with them and played around a bit with using an oscilloscope and some FETs to write and read them.

You can buy core memory kits [1] for adding core memory to an arduino. They only give 8x4 but you could get to "cordmp" with a five-bit encoding ;-)

The vendor, with whom I have absolutely no affiliation except for exchanging a few emails a several years ago, based his kits on a project that I did with a friend a long time ago [2].

It was a fun project that had interesting analog and digital sides to it.

[1] https://www.tindie.com/products/kilpelaj/core-memory-shield-...

[2] https://corememoryshield.com/

Oh very nice thanks :) It would feel a bit like cheating though to just buy a ready made kit ;)

I wonder how they assemble the cores and the wires efficiently, because that was always the most painful part when working with the cores.

Edit: Typos

Threading the cores is indeed quite fiddly. I think back in the day, large numbers of seamstresses pivoted into manufacturing core memory!

If I recall correctly, the weaving was often done in Malta as it was the only place where the carpet weavers had fingers nimble enough to do it.

(edit) a bit of digging around turned up an article [0] showing women building core memory for the Apollo Guidance Computer.

[0] https://www.amusingplanet.com/2020/02/that-time-when-compute...

There's some really good core assembly footage in this old Sperry-Rand film: https://youtu.be/s39Dzei2Z2I?t=92

I had some confusion in really understanding how the core memory worked from the author's brief description, and I decided that's something I should remedy. This video has a good explanation, with good figures and animations explaining it (the how part starts at 2:45): https://www.youtube.com/watch?v=AwsInQLmjXc

I bought a core memory board in a Philadelphia tech junkyard in the late '80s. It probably cost around $5. It's my favorite artifact from the era in which I became a software developer. When I started a performing arts organization in 2017, I named it Core Memory Music. The name confuses the heck out of everyone, which is fine by me. :)

https://www.corememorymusic.com

If curious see also

a thread from 2017: https://news.ycombinator.com/item?id=14485789

I think core memory is fascinating. It has a long history of interesting applications (including the Apollo space missions) but is largely disused today.

The article discusses wiring up your own 1-bit core memory within which you can store any bit you'd like. :)

https://en.wikipedia.org/wiki/Magnetic-core_memory

If anyone is curious what a megabyte of core would look like, see page 732 of "Engineering and Operations in The Bell System", second edition. It has a drawing showing memory cards from their electronic switching systems from 1965 through 1984. Here's a photo of that page [1].

In 1965 they introduced ferrite sheets, and a 1.18 MB memory card was 104 feet long.

1971 brought ferrite cores, and that same storage fit on a card under 9 feet long.

https://imgur.com/gallery/z8nJo3T

This page has nice pictures of two types of memory used in some tabletop calculators in the 60s. (I find the mechanical delay line memory especially fascinating.)

http://www.vintagecalculators.com/html/calculator_memory_tec...

It's weird that my university textbooks treat core memory as the de facto way computers stored data for immediate use (after it was read from the the drum or {magnetic|paper} tape). Now it's up there with Nixie tubes and penny-farthing racing as some sort of retro hobby thing (although Nixie tubes are way more aesthetically pleasing). I feel old now. Get off my lawn.

Is this the Wayne Holder of Dungeon Master fame?

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