Energy-delay Tradeoff Research Articles

Designing leakage tolerant, low power wide-OR dominos for sub-130 nm CMOS technologies

In this paper, we discuss the design of leakage tolerant wide-OR domino gates for deep submicron (DSM), bulk CMOS technologies. Technology scaling is resulting in a 3×–5× increase in transistor IOFF/μm per generation causing 15–30% degradation in the noise margin of high performance domino gates. We investigate several techniques that can improve the noise margin of domino logic gates and thereby ensure their reliable operation for sub-130nm technologies. Our results indicate that, selective usage of dual VTH transistors shows acceptable energy-delay tradeoffs for the 90nm technology. However, techniques like supply voltage (Vcc) reduction or using non-minimum Le transistors are required in order to ensure robust and low power operation of wide-OR domino designs for the 70nm generation.

Methods for true energy-performance optimization

This paper presents methods for efficient energy-performance optimization at the circuit and micro-architectural levels. The optimal balance between energy and performance is achieved when the sensitivity of energy to a change in performance is equal for all the design variables. The sensitivity-based optimizations minimize energy subject to a delay constraint. Energy savings of about 65% can be achieved without delay penalty with equalization of sensitivities to sizing, supply, and threshold voltage in a 64-bit adder, compared to the reference design sized for minimum delay. Circuit optimization is effective only in the region of about /spl plusmn/30% around the reference delay; outside of this region the optimization becomes too costly either in terms of energy or delay. Using optimal energy-delay tradeoffs from the circuit level and introducing more degrees of freedom, the optimization is hierarchically extended to higher abstraction layers. We focus on the micro-architectural optimization and demonstrate that the scope of energy-efficient optimization can be extended by the choice of circuit topology or the level of parallelism. In a 64-bit ALU example, parallelism of five provides a three-fold performance increase, while requiring the same energy as the reference design. Parallel or time-multiplexed solutions significantly affect the area of their respective designs, so the overall design cost is minimized when optimal energy-area tradeoff is achieved.

A Distributed Scheme for Achieving Energy-Delay Tradeoffs With Multiple Service Classes Over a Dynamically Varying Network

We consider a dynamical probabilistic traffic model for the number of users transmitting at any time. This model captures both user mobility and traffic burstiness. Moreover, we assume no centralized controller, such as a scheduler, is available. When multiple users transmit simultaneously, multiple-access interference (MAI) affects throughput considerably. Most queue control schemes assume individual users know the states of their own queues (local queue information) along with the states of other users queues (shared queue information) and address issues of scheduling; but this sharing of information may be onerous in a practical system. While shared queue information has recently been shown (Me/spl acute/dard et al., 2004) not to affect the capacity of such systems, it has a considerable impact on delay. We introduce a scheme, where for each user, a bit of shared queue information specifies whether its queue length is above or below a threshold. Our scheme relies on two different service classes implemented through a superposition coding scheme (first proposed with Me/spl acute/dard and Goldsmith, 1999, further studied and expanded with Me/spl acute/dard et al., 2004). The first class experiences no delay due to multiple-access interference, while the second class requires retransmissions when such an event occurs. We show how our scheme affords an energy-delay tradeoff. Moreover, when configured properly, our scheme can attain boundary points of the region corresponding to minimum energy with no shared queue information for zero delay along with minimum energy subject to system stability. We derive bounds on the performance of the multiple-access system using our proposed scheme by introducing Lyapunov function bounds in a manner similar to Bertsimas et al., 2001.