Multiple-Precision Fixed-Point Vector Multiply-Accumulator Using Shared Segmentation

This paper presents a 64-bit fixed-point vector multiply-accumulator (MAC) architecture capable of supporting multiple precisions. The vector MAC can perform one 64x64, two 32x32, four 16x16 or eight 8x8 bit signed/unsigned multiply-accumulates using essentially the same hardware as a scalar 64-bit MAC and with only a small increase in delay. The scalar MAC architecture is “vectorized” by inserting mode-dependent multiplexing into the partial product generation and by inserting mode-dependent kills in the carry chain of the reduction tree and the final carry-propagate adder. This is an example of "shared segmentation" in which the existing scalar structure is segmented and then shared between vector modes. The vector MAC is area efficient and can be fully pipelined which makes it suitable for high-performance processors and possibly dynamically reconfigurable processors.