SPIM (Stanford Pipelined Iterative Multiplier): A Pipelined 64 X 64 Bit Iterative Multiplier

: A 64 by 64 bit iterating multiplier, SPIM (Stanford Pipelined Iterative Multiplier) is presented. The pipelined array consists of a small tree of 4:2 adders. The 4:2 tree is better suited than a Wallace tree for a VLSI implementation because it is a more regular structure. A 4:2 carry save accumulator at the bottom of the array is used to iteratively accumulate partial products, allowing a partial array to be used, which reduces area. SPIM was fabricated in a 1.6 micron CMOS process. It has a core size of 3.8 X 6.5mm and contains 41 thousand transistors. The on chip clock generator runs at an internal clock frequency of 85MHz. The latency for a 64 X 64 bit fractional multiply is under 120ns, with a pipeline rate of one multiply every 47ns.