A WORKING USB DRIVE WITH MAGNETIC CORE MEMORY IS REAL
A working USB drive that stores data in hand-assembled magnetic core memory — all 64 bits of it.
by polymatt
Science
Built withESP32
- difficulty
- ●●●●●
- time
- several weekends
- license
- license not specified
- repo
- repo 0 stars
●●●●● · several weekends · license not specified · 0 stars · repo
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COMPAREE VERDICT
This is a beautiful museum piece, not a practical build you can replicate this weekend. polymatt milled two PCBs on a small CNC router, paired a 64-bit core memory array with L293 H-bridge drivers and an ESP32 that handles USB, and filled the enclosure with silicone oil to keep the cores at a steady temperature. It is wildly impractical, since the memory the ESP32 needs just for its USB stack is many times larger than the core array, but that is the entire appeal. The build is shown in polymatt's video and summarised by Hackaday, but we could not find published PCB files, firmware source or a parts list: neither the video description nor the Hackaday article links any. If you want to build something similar, you will be working from the video and core memory theory, designing the core assembly, the driver logic and the voltage tuning yourself. The thing most likely to go wrong is spending money on core memory and H-bridge ICs before you have a working driver design.
IN THE REPO
GOOD TO KNOW
- —Neither the Hackaday article nor the video description links a repository or design files
- —We found no CAD files, PCB Gerbers, firmware source or bill of materials
- —The build is shown in polymatt's YouTube video (with fabrication and core chapters) and summarised by Hackaday
- —No licence is stated, because no design files are published
- —Components named in the coverage: ESP32 module, L293 H-bridge ICs, two CNC-milled PCBs, silicone oil, an enclosure with an acrylic window, and the core memory itself
- —The video description lists KiCad for PCB design, the Arduino IDE for firmware and a Carvera Air desktop CNC
Parts to buy
7 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Videos
Memory is crazy expensive so I made my own…23:32
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Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Watch polymatt's build video and read the Hackaday write-up (The video shows the concept, fabrication and the cores; the Hackaday article summarises it. No design files are linked from either)
- 2.Research magnetic core memory read/write principles and destructive read cycles(You will need to understand the theory before designing the driver logic)
- 3.Design or source a core memory array — 64 bits is small, but hand-assembly is tedious(Vintage core memory turns up on the second-hand market, or you can thread your own ferrite cores)
- 4.Design the driver PCB with L293 H-bridges and sense line circuitry(Voltage levels have to be tuned experimentally, as the article describes)
- 5.Write ESP32 firmware for USB mass storage emulation and core memory interfacing(The memory the ESP32 needs just for its USB stack is many times larger than the storage you are driving, which is part of the absurdity)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
KNOWN ISSUES
- We found no published firmware, PCB files or parts list beyond the components named in the video and the Hackaday article, so you are rebuilding from a description, not cloning a repo
- Core memory samples are not common parts — sourcing vintage cores or winding your own is a project within the project
- Destructive read logic is not trivial — every read erases the bit, so the firmware has to restore it immediately, which requires careful timing and sense line conditioning
- Drive voltage has to be found experimentally: too low and the cores do not flip, too high and you start disturbing neighbouring cores. The coverage does not give the exact values
- The silicone oil fill is probably overkill for function, and it means building an enclosure with an acrylic window that holds oil without leaks or trapped air
- This is not a USB drive you would actually use: 64 bits is 8 bytes, and the memory the ESP32 needs just for its USB stack is many times larger than the core array
Can I actually build this without published design files?
Only if you are comfortable designing PCBs, writing ESP32 USB firmware, and researching core memory driver circuits from first principles. This is not a weekend kit build.
Where do I get magnetic core memory?
polymatt's build video links a vintage core memory reference, and Tom's Hardware reports the cores were salvaged from an old Russian computer. Vintage core planes turn up on the second-hand market; winding your own means threading wires through tiny ferrite rings by hand.
What is a destructive read and why does it matter?
Reading a core memory cell flips the bit to zero, so you have to immediately write it back if it was a one. This requires extra circuitry and careful firmware logic.
Is the silicone oil necessary?
No — it helps stabilise core temperature for more reliable bit flipping, but the article suggests it is probably overkill for a 64-bit array. It does look cool through the acrylic window.
How much does this actually store?
64 bits, or 8 bytes. This is art, not storage.
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Discussion1
FROM THE COMPAREE TEAM
64 bits of storage, hand-assembled cores, destructive reads, and silicone oil stabilisation — all to make a USB drive that holds less than a tweet. What would you actually store on it?
polymatt
polymatt is a maker YouTuber who documented this build in a 23-minute video, from the core memory concept through CNC-milled PCBs to the finished drive. The result is a working USB device that stores 64 bits, less than a single tweet, using magnetic cores and destructive-read logic.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM1d ago
Practical notes from our verification: neither the Hackaday article nor polymatt's video description links PCB files, firmware source or a parts list, so beyond the named components (ESP32, L293 H-bridges, core memory, silicone oil) you are on your own. The build is real and well shown in the video, but this is not a project you can clone: you would have to recreate it from the video and core memory theory. The appeal is not diminished by the lack of files; if anything, hand-building this from principles makes it more impressive. If you want to attempt something similar, start with core memory theory and driver design before spending money on vintage cores or H-bridge ICs.