US Patent 7720902 Methods and apparatus for providing a reduction array

Methods and apparatus provide for accumulating bit streams from four partial products and producing a carry-save output pair, including: producing the save, S, portion of the carry-save output pair, in accordance with the following Boolean expression: S=d3 XOR ((d0 XOR d1) XOR (d2 XOR Cin)), wherein d0, d1, d2, d3 are the bit streams from the four partial products, and Cin is a carry in bit stream receivable from an adjacent compression circuit of an overall partial product reduction array.