What is Magnetic-core memory?
-Core memory uses - toroids - (rings) of a - hard - magnetic material - (usually a - semi-hard - ferrite). Each core stores one - bit - of information. Two or more wires pass through each core, forming an - X-Y array of cores. When an electrical current above a certain - threshold is applied to the wires, the core will become magnetized. - The core to be written is selected by powering one X and one Y wire - to half of the required power, such that only the single core at the - intersection is written. Depending on the direction of the currents, - the core will pick up a clockwise or counterclockwise magnetic field, - storing a 1 or 0. - - This writing process also causes electricity to be - induced - into nearby wires. If the new pulse being applied in the X-Y wires is - the same as the last applied to that core, the existing field will do - nothing, and no induction will result. If the new pulse is in the - opposite direction, a pulse will be generated. This is normally - picked up in a separate "sense" wire, allowing the system - to know whether that core held a 1 or 0. As this readout process - requires the core to be written, this process is known as - destructive - readout, and requires additional circuitry to reset the core to - its original value if the process flipped it. -
-