An interactive visual demonstration of how magnetic core memory worked, using a 4×4 ferrite core matrix.
Magnetic core memory was the dominant form of computer memory from the mid-1950s through the mid-1970s. It stored data by magnetizing tiny ferrite rings (cores) threaded onto a grid of wires. Each core could be magnetized in one of two directions — clockwise (1) or counterclockwise (0).
Core memory uses coincident current addressing: two wires (X and Y) pass through each core. Neither wire alone carries enough current to flip a core's magnetic state — only where both wires intersect does the combined current reach the threshold needed to change a bit.
This visualizer lets you:
- Select X and Y wires to energize them with half-current
- Observe how only the core at the intersection receives full current
- Write 1 or 0 to the targeted core and watch the magnetic field direction change
- Click any core to inspect its current state
Open index.html in a browser. No build tools or dependencies required.
Open the index.html file directly, or view the source on GitHub.
MIT