Introducing KeyRing self-timed microarchitecture and timing-driven design flow

A self-timed microarchitecture called KeyRing is presented, and a method for implementing KeyRing circuits compatible with a timing-driven electronic design automation (EDA) flow is discussed. The KeyRing microarchitecture is derived from the AnARM, a low-power self-timed ARM processor based on ad hoc design principles. First, the unorthodox design style and circuit structures are revisited. A theoretical model that can support the design of generic circuits and the elaboration of EDA methods is then presented. Also addressed are the compatibility issues between KeyRing circuits and timing-driven EDA flows. The proposed method leverages relative timing constraints to translate the timing relations in a KeyRing circuit into a set of timing constraints that enable timing-driven synthesis and static timing analysis. Finally, two 32-bit RISC-V processors are presented; called KeyV and based on KeyRing microarchitectures, they are synthesized in a 65 nm technology using the proposed EDA flow. Postsynthesis results demonstrate the effectiveness of the design methodology and allow comparisons with a synchronous alternative called SynV. Performance and power consumption evaluations show that KeyV has a power efficiency that lies between SynV with clock-gating and SynV without clock-gating.