An area- and energy-efficient asynchronous Booth multiplier for mobile devices

The recent explosion in the number of handheld multimedia devices has created a need for energy-efficient computation due to limited battery lifetimes. We focus on multiplication, which is needed in several application domains, e.g., 3D graphics, signal processing, and cryptography. We introduce an asynchronous implementation of a plain Booth multiplier (i.e., radix-2), which is both area- and energy-efficient, and therefore suitable for mobile applications. This paper makes the following contributions. First, a novel counterflow organization is introduced, in which the data bits flow in one direction, and the Booth commands piggyback on the acknowledgments flowing in the opposite direction. Second, the arithmetic and shifter units are merged together to obtain significant improvement in area, energy as well as speed. Third, our design performs overlapped execution of multiple iterations of the Booth algorithm. Finally, the design is quite modular, which allows scaling to arbitrary operand widths, without gate resizing or cycle time overheads. Spice simulations in a 0.18 μm TSMC process at 1.8 V, indicate promising performance: the multiplier takes 1.08 ns per Booth iteration, regardless of the operand widths, thereby demonstrating the scalability of our approach. In addition, the multiplier is fully functional at reduced supply voltages (e.g., 1.0 V), and thus capable of dynamically trading off performance for energy efficiency.