CAD directions for high performance asynchronous circuits

This paper describes a novel methodology for high performance asynchronous design based on timed circuits and on CAD support for their synthesis using Relative Timing. This methodology was developed for a prototype iA32 instruction length decoding and steering unit called RAPPID ("Revolving Asynchronous Pentium® Processor Instruction Decoder") that was fabricated and tested successfully. Silicon results show significant advantages - in particular, performance of 2.5-4.5 instructions per nS - with manageable risks using this design technology. RAPPID achieves three times faster performa the power and requiring a minor area penalty as a comparable 400MHz clocked circuit. Relative Timing is based on user-defined and automatically extracted relative tinning assumptions between signal transitions in a circuit and its environment. It supports the specification, synthesis, and verification of high-performance asynchronous circuits, such as pulse-mode circuits, that can be derived from an initial speed-independent specification. Relative timing presents a "middle-ground" between clocked and asynchronous circuits, and is a fertile area for CAD development. We discuss possible directions for future CAD development.