Automating RT-level operand isolation to minimize power consumption in datapaths

Designs which do not fully utilize their arithmetic datapath components typically exhibit a significant overhead in power consumption. Whenever a module performs an operation whose result is not used in the downstream circuit, power is being consumed for an otherwise redundant computation. Operand isolation is a technique to minimize the power overhead incurred by redundant operations by selectively blocking the propagation of switching activity through the circuit. This paper discusses how redundant operations can be identified concurrently to normal circuit operation, and presents a model to estimate the power savings that can be obtained by isolation of selected modules at the register-transfer (RT) level. Based on this model, an algorithm is presented to iteratively isolate modules, while minimizing the cost incurred by RTL operand isolation. Experimental results with power reductions of up to 30% demonstrate the effectiveness of the approach.