Core memory (and other uses of ferrite cores in computers)

Continuing the discussion from The Apollo Guidance Computer:

As I recall, the origin story for ferrite cores as computer memory involves the search for, or discovery of, materials with high enough hysteresis to do the job, where previous applications had been searching for materials with low hysteresis. However, this is a rabbit hole, as the discoveries and inventions led to fights:

Forrester has since observed, “It took us about seven years to convince the industry that random-access magnetic-core memory was the solution to a missing link in computer technology. Then we spent the following seven years in the patent courts convincing them that they had not all thought of it first.”

Here’s a substantial reference page, from Brent Hilpert’s Early Digital Electronics site:

And a couple of images from it:

The CHM has this to say:

Amateur inventor Frederick W. Viehe filed a core memory patent in 1947 followed by Harvard physicist An Wang in 1949. RCA’s Jan Rajchman and MIT’s Jay Forrester filed in 1950 and 1951 respectively. Other important contributors include E. Albers-Schönberg, J. P. Eckert, and M. K. Haynes. Led by Forrester, the Whirlwind computer project at Massachusetts Institute of Technology for a U.S. Navy real-time flight simulator replaced a troubled electrostatic CRT memory with a 32 by 32 array (called a plane) of 1024 cores and demonstrated its advantages for the first time in August 1953.


Speaking of cores, don’t forget this great instructional film by the US Army (1961). It not only explains the principles, but also how they may be used as switching devices in circuits (the soviet ternary SETUN was built of elements like these).




From my private collection: Part of a IBM /360 core memory:


There’s something about a core store that I had to keep this one:-

^^^ 4K by 12 bits core store from a PDP 8, dated 1973. (Oops, it’s upside down.)

Interesting short page on core and rope memories.

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Here’s a remarkable solid-state inductive ROM: the one inside HP’s desktop computer/calculator, the 9100. It’s a 16-layer PCB which uses stray inductance to hold the ROM bits.

the HP 9100A’s processor was actually a microprogrammed state machine and didn’t run software in the conventional sense, state-machine design can employ a control ROM to direct the machine’s operations during each state, to test branch conditions, and to specify a next state. Osborne determined that the HP 9100A would, at a minimum, need a 32-kbit ROM, organized as 512 64-bit words. The HP 9100A could have used more ROM capacity, but even 32 kbits was well beyond the state of the art for 1965-era electronics. In fact, it was completely beyond the reach of the integrated-circuit technology in 1965, which was barely able to pattern 50 devices (transistors, diodes, and resistors) on one chip.