Computationally-redundant energy-efficient processing for y'all (CREEPY)

Abstract

Dennard scaling has ended. Lowering the voltage supply (Vdd) to sub volt levels causes intermittent losses in signal integrity, rendering further scaling (down) no longer acceptable as a means to lower the power required by a processor core. However, if it were possible to recover the occasional losses due to lower Vdd in an efficient manner, one could effectively lower power. In other words, by deploying the right amount and kind of redundancy, we can strike a balance between overhead incurred in achieving reliability and savings realized by permitting lower Vdd. One promising approach is the Redundant Residue Number System (RRNS) representation. Unlike other error correcting codes, RRNS has the important property of being closed under addition, subtraction and multiplication. Thus enabling correction of errors caused due to both faulty storage and compute units. Furthermore, the incorporated approach uses a fraction of the overhead and is more efficient when compared to the conventional technique used for compute-reliability. In this article, we provide an overview of the architecture of a CREEPY core that leverages this property of RRNS and discuss associated algorithms such as error detection/correction, arithmetic overflow detection and signed number representation. Finally, we demonstrate the usability of such a computer by quantifying a performance-reliability trade-off and provide a lower bound measure of tolerable input signal energy at a gate, while still maintaining reliability.