1964- Ferrite Core Memory CDC 6600
1964- Magnetic core memory, or ferrite-core memory (CDC 6600), is an early form of random access computer memory. It uses small magnetic ceramic rings, the cores, through which wires are threaded to store information via the polarity of the magnetic field they contain. Such memory is often just called core memory, or, informally, core.
Core relies on the hysteresis of the magnetic material used to make the rings. Only a magnetic field over a certain intensity (generated by the wires through the core) can cause the core to change its magnetic polarity. To select a memory location, one of the X and one of the Y lines are driven with half the current required to cause this change. Only the combined magnetic field generated where the X and Y lines cross is sufficient to change the state; other cores will see only half the needed field, or none at all. By driving the current through the wires in a particular direction, the resulting induced field forces the selected core's magnetic field to point in one direction or the other (north or south).
This core was from the CDC 6600, a mainframe computer from Control Data Corporation, first delivered in 1964. It is generally considered to be the first successful supercomputer, outperforming its fastest predecessor, IBM 7030 Stretch, by about three times. It remained the world's fastest computer from 1964 to 1969, when it relinquished that status to its successor, the CDC 7600.
The system organization of the CDC 6600 was used for the simpler (and slower) CDC 6400, and later a version containing two 6400 processors known as the CDC 6500. These machines were instruction-compatible with the 6600, but ran slower due to a much simpler and more sequential processor design. The entire family is now referred to as the CDC 6000 series. The CDC 7600 was originally to be compatible as well, starting its life as the CDC 6800, but during the design compatibility was dropped in favor of outright performance. The 7600 and 6600 were binary compatible, but the software developed in Sunnyvale was not compatible on the two machines.
