Very high radix square root with prescaling and rounding and a combined division/square root unit

摘要

An algorithm for square root with prescaling and selection by rounding is developed and combined with a similar scheme for division. Since division is usually more frequent than square root, the main concern of the combined implementation is to maintain the low execution time of division, while accepting a somewhat larger execution time for square root. The algorithm is presented in detail, including the mathematical development of bounds for the first square-root digit and for the scaling factor. The proposed implementation is described, evaluated and compared with other combined div/sqrt units. The comparisons show that the proposed scheme potentially produces a significant speed-up for division, whereas, for square root, the speed-up is small.