A Synthesisable Quasi-Delay Insensitive Result Forwarding Unit for an Asynchronous Processor

The implementation of an efficient result forwarding unit for asynchronous processors faces the problem of the inherent lack of synchronisation between result producer and consumer units. An efficient, full-custom solution to this problem has been proposed and implemented before (in the AMULET3 asynchronous processor) with the consequent limitations on design-space exploration and technology portability. The use of automatic synthesis to describe asynchronous systems is attractive in terms of rapid development, technology mapping transparency and design space exploration. This paper presents the description of a synthesisable result forwarding unit for an asynchronous microprocessor, using the syntax-directed synthesis approach and targeting a robust quasi-delay-insensitive implementation. The description of such a system also serves as a complex case study to evaluate the capabilities and limitations of syntax-directed synthesis when used as a tool to automate the synthesis of performance-demanding asynchronous systems.