A Comparative Study of subword parallel adders for multimedia applications

Subword parallelism can efficiently improve the performance of multimedia applications. Two different control mechanisms, carry truncation and carry elimination, for subword parallel adder design are proposed in this paper. The carry truncation mechanism achieves subword partition by inserting killing logics into the carry propagation chain, while the carry elimination one employs control logics on the subword boundary bit positions. Based on these two mechanisms, we implement several representative adder algorithms. The experimental results show that, for all the adder algorithms, the proposed carry elimination mechanism counts averagely 8% less delay than the carry truncation one. However, except for the Kogge-Stone and Brent-Kung adders, the carry elimination mechanism requires more gates and higher power consumption than the carry truncation one. This paper also compares the performance of different adder algorithms.