Population count circuits for Associative Memories: A comparison study

This paper proposes a novel population count circuit for Associative Memories (AM)s. Currently, AM chips requires a large number of silicon area for the population count circuitry. For this reason, is necessary an optimization in terms of area for the future AM devices to have a better memory density. A population count circuit counts how many blocks of the AM are in a matching state. If the count sum is greater than a preconfigured threshold, the output wire is set to `1', otherwise is set to `0'. In the existing circuits there are, in addition, several control signals that are used to increase the circuit flexibility, but these controls require a large number of transistors and interconnections. The purpose of the proposed circuit is to reduce the number of transistors and interconnections complexity, with the final aim to reduce the occupied silicon area.