A 28.5mW 2.8GFLOPS floating-point multifunction unit for handheld 3D graphics processors

Abstract

A low-power, high-performance 4-way 32-bit floating-point multifunction unit is developed for handheld 3D graphics processors. It uses logarithmic arithmetic to unify matrix, vector, and elementary functions into a single arithmetic unit. The optimal designs of logarithmic and antilogarithmic converters are presented. An adaptive number conversion scheme is proposed and it reduces total area by 15%. With this scheme, the matrix-vector multiplication (MAT), cross-product, lerp, and logarithm (logx y with 2 variables) are newly unified with the other operations. The unit achieves 2-cycle throughput for the MAT and single-cycle throughput for all other operations. It takes 451 K transistors and achieves 2.8 GFLOPS at 200 MHz with 28.5 mW power consumption.