Dynamic Functional Unit Assignment for Low Power

Abstract

A hardware method for functional unit assignment is presented, based on the principle that a functional unit's power consumption is approximated by the switching activity of its inputs.Since computing the Hamming distance of the inputs in hardware is expensive, only a portion of the inputs are examined. Integers often have many identical top bits, due to sign extension, and floating points often have many zeros in the least significant digits, due to the casting of integer values into floating point, and other reasons. The accuracy of these approximations is studied and the results are used to develop a simple, but effective, hardware scheme.

Functional Unit Selection in Superscalar Microprocessors for Low Power

“…This technique can be implemented together with other power-saving techniques like DVS [4] and FU assignment [2], so whatever power saving achieved here is an extra gain. What is more, the overall performance is not harmed, thanks to the scheduling algorithm.…”

“…Recently, various power reduction techniques targeting on issue queue [1], execution core [2], cache structure [3] and other components inside a processor have been proposed. Apart from them, a most widely used technique is Dynamic Voltage Scaling (DVS) [4], which is based on the observation that maximum performance is not always necessary and by cleverly lowering the performance level here and there, the overall energy consumption can be reduced.…”

Power efficient dynamic-range utilisation for DSP on FPGA

“…Effective dynamic-range detection methods are well developed [2] and specific techniques to use it to reduce the adverse effect of underutilisation on power are proposed in [2], [8]. Dynamic functional unit scheduling [9] can reduce input transitions whereas Booth decoding [10] can increase the probability of zero partial products. Microprocessor operation stacking [12] reduces redundancy but introduces scheduling issues and requires processor modification.…”

Energy-aware opcode design

“…They indicate that switching in the register-port increases the instruction-energy by 10%. Similarly, Haga et al [4] explore dynamically assigning function-units to reduce switching. They show a 26% power reduction in integer ALU.…”