Victor GijsbersJan 3, 2023
Looking for people who know something about early computing, especially in the Netherlands. Please boost and help me solve the mystery of this custom made plate that used to belong to my grandfather Bram Jan Loopstra, one of the pioneers of Dutch computing. What do the pictures mean? #computing #history (EDIT: Wow, thanks for the overwhelming response! You may have to check the post on my instance to see all the MANY helpful reactions.)
Show threadRaygan Kelly 
@victorgijsbers I'm not an expert but I can guess that the top image is an illustration or diagram of magnetic core memory https://en.wikipedia.org/wiki/Magnetic-core_memory
Magnetic-core memory - Wikipedia

Jan 3, 2023 at 3:10pmWeb
Show threadVictor GijsbersJan 3, 2023
@raygan Interesting! My mother also found this, do you think it's a magnetic core memory (turned into a paperweight)?
Show threadRaygan Kelly Jan 3, 2023
@victorgijsbers I'd bet on it! Looks just like some images I've seen.
Show threadRaygan Kelly Jan 3, 2023
@victorgijsbers this is a really neat paperweight! If you look closely you can see the magnetic toroids, and it’s 16 x 16 which (I think) means this is 256 bits, or 32 bytes.
Show threadStephen ShanklandJan 3, 2023
@raygan @victorgijsbers Sure looks like core memory to me. Here's some IBM core memory from days of yore, on display at Computer History Museum. 1536 bits. https://flickr.com/photos/shankrad/52598590820/
IBM Model 64 magnetic core plane, 1536 bits

Flickr
Show threadWim🧮Jan 3, 2023

@stshank
The drawing on the right is the magnetic hysteresis loop, that is what allows the ferrite cores to "remember" information.

@raygan @victorgijsbers

Show threadRaygan Kelly Jan 3, 2023

@wim_v12e @stshank @victorgijsbers Very cool!

I'd bet that the two dot grid patterns indicate two states of the 100-bits of memory above, maybe encoding a message, but I don't know how to go any further toward understanding what they might mean.

Show threadRaygan Kelly Jan 3, 2023
@wim_v12e @stshank @victorgijsbers Also the drawing at the left is almost certainly a circuit diagram symbol but I'm not sure for what. Looks similar to the ones in the top right corner here:
Show threadResunaJan 3, 2023
@victorgijsbers @raygan I have a core from a CDC 6400 that looks just like that. Also this Siemens 256k core.
Show threadRaygan Kelly Jan 3, 2023
@resuna @victorgijsbers No one will ever need more than 256k of RAM.
Show threadstoneheadJan 3, 2023
@victorgijsbers @raygan It is. We had something similar at De Jonge Onderzoekers Nijmegen. Each core is one bit, so you couldn't store even this post in there ☺️
https://en.wikipedia.org/wiki/Magnetic-core_memory
Magnetic-core memory - Wikipedia

Show threadA Cyber ExpertJan 3, 2023

@victorgijsbers @raygan

Correct, that is a piece of magnetic core memory.

Show threadMichael WinibergJan 3, 2023

@victorgijsbers @raygan

definitely

Show threadDan FitzGeraldJan 3, 2023
@victorgijsbers @raygan IBM had a long tradition of packaging defective components in acrylic plastic to use as paperweights
Show threadEll 🏳️‍⚧️Jan 4, 2023
@victorgijsbers @raygan That is most defintiely magnetic core memory, yep!
Show threadEll 🏳️‍⚧️Jan 4, 2023
@victorgijsbers @raygan It's a 16x16 grid, so 256 bits (32 bytes!) of memory. The grid with the diagonally-mounted cores, and the sense wire snaking willy-nilly through all of them, are textbook core memory.
Show threadMartin KleppmannJan 4, 2023
@victorgijsbers @raygan Yes, that’s 256 bits of core memory