Improved Architectures for a Floating-Point Fused Dot Product Unit

This paper presents improved architectures for a floating-point fused two-term dot product unit. The floating-point fused dot product unit is useful for a wide variety of digital signal processing (DSP) applications including complex multiplication and fast Fourier transform (FFT) and discrete cosine transform (DCT) butterfly operations. In order to improve the performance, a new alignment scheme, early normalization, a four-input leading zero anticipation (LZA), a dual-path algorithm, and pipelining are applied. The proposed designs are implemented for single precision and synthesized with a 45nm standard cell library. The proposed dual-path design reduces the latency by 25% compared to the traditional floating-point fused dot product unit. Based on a data flow analysis, the proposed design can be split into three pipeline stages. Since the latencies of the three stages are fairly well balanced, the throughput is increased by a factor of 2.8 compared to the non-pipelined dual-path design.