Associative capabilities for mass storage through array organization

Since computers first came into wide usage, digital systems designers have been intrigued by the possibilities of associative or content addressable memories. The concept is quite easy to understand; whereas, in the conventional case, the address is furnished to the memory and the data stored at that location is the expected result, in the associative reference, the data is furnished and the expected result is a list of all addresses which contain matching data. Up to now, however, the physical systems which exhibit the requisite symmetry to realize this concept have been necessarily very costly because the commonly used, low cost, random access memories do not easily lend themselves to this new operation. Those digital systems designers who predicted widespread use of associative memories by the late 1960's are found in retrospect to have seriously underestimated the difficulty in implementing thin magnetic film or superconducting memory systems, on which these forecasts heavily depended.