Design of High Speed 128 bit Parallel Prefix Adders

In this paper, we propose 128-bit Kogge-Stone, Ladner-Fischer, Spanning tree parallel prefix adders and compared with Ripple carry adder. In general N-bit adders like Ripple Carry Adders (slow adders compare to other adders), and Carry Look Ahead adders (area consuming adders) are used in earlier days. But now the most Industries are using parallel prefix adders because of their advantages compare to other adders. Parallel prefix adders are faster and area efficient. Parallel prefix adder is a technique for increasing the speed in DSP processor while performing addition. While when we want to design any 128-bit operating systems and processors we can use these adders in place of regular adders. We simulate and synthesis different types of 128-bit prefix adders using Xilinx ISE 12.3 tool. By using these synthesis results, we noted the performance parameters like number of LUTs and delay. We compare these three adders in terms of LUTs (represents area) and delay values. Keywords− prefix adder, carry operator, Kogge-Stone, Spanning tree, Ladner-Fischer.