Power and Area-Efficient Approximate Wallace Tree Multiplier for Error-Resilient Systems

Kartikeya Bhardwaj1,  Pravin Mane2,  Joerg Henkel3
1Electrical & Electronics Engineering, BITS Pilani-Goa Campus, Goa-403726, India, 2Electrical & Electronics Engineering, BITS Pilani – Goa Campus Goa -403726 India, 3Department of Computer Science, Karlsruhe Institute of Technology, Karlsruhe, Germany


Today in sub-nanometer regime, chip/system designers add accuracy as a new constraint to optimize Latency-Power- Area (LPA) metrics. In this paper, we present a new power and area-efficient Approximate Wallace Tree Multiplier (AWTM) for error-tolerant applications. We propose a bit-width aware approximate multiplication algorithm for optimal design of our multiplier. We employ a carry-in prediction method to reduce the critical path. It is further augmented with hardware efficient precomputation of carry-in. We also optimize our multiplier design for latency, power and area using Wallace trees. Accuracy as well as LPA design metrics are used to evaluate our approximate multiplier designs of different bit-widths, i.e. 4 × 4, 8 × 8 and 16 × 16. The simulation results show that we obtain a mean accuracy of 99.85% to 99.965%. Single cycle implementation of AWTM gives almost 24% reduction in latency. We achieve significant reduction in power and area, i.e. up to 41.96% and 34.49% respectively that clearly demonstrates the merits of our proposed AWTM design. Finally, AWTM is used to perform a real time application on a benchmark image. We obtain up to 39% reduction in power and 30% reduction in area without any loss in image quality.