Core Memory Block
Ferrite is iron. This form of computer memory was widely used
through the late 1950's to the early 1970's. This memory block
can store up to 32 bits, or four characters. The "On"
or "Off" switches are created by having an iron
magnet in the shape of a donut intersected by horizontal and
vertical wires. The "1" and "0" switch
setting was created by alternating the direction of the positive
and negative currents.
Core memory was a great step forward in memory technology
in the 1960's. It was the first memory technology that had
a decent quantity of memory in a practical size, power requirements
and speed. Prior to core memory, the dominant technologies
were magnetic drum memory, electrostatic memory, and (rarely)
mercury delay line memory. Core technology was the first to
allow memory to have the reliability of solid state electronics.
It could be hand assembled for about a penny a bit, and retained
what it stored despite power failures.
This 4K memory core block with a 22-bit word size was removed
from a Daystrom-046 computer built in San Diego in 1957. This
particular Daystrom was used at National Steel in Detroit,
Michigan to check 300 process control points. The system would
check approximately 40-150 points per hour. The Daystrom 046
computer system cost $300,000 without peripherals.