A Clockless Computing System based on the Static Dataflow Paradigm

The ambitious challenges posed by next exascale computing systems may require a critical re-examination of both architecture design and consolidated wisdom in terms of programming style and execution model, because such systems are expected to be constituted by thousands of processors with thousands of cores per chip. But how to build exascale architectures remains an open question. This paper presents a novel computing system based on a configurable architecture and a static dataflow execution model. We assume that the basic computational unit is constituted by a dataflow graph. Each processing node is constituted by an ad hoc kernel processor - designed to manage and schedule dataflow graphs, and a manycore dataflow execution engine - designed to execute such dataflow graphs. The main components of the dataflow execution engine are the Dataflow Actor Cores (DACs), which are small, identical and configurable. The major contributions of this paper are: i) the introduction of a machine language (named D#) which represents the low-level static configuration information of the system; ii) the introduction of a self-scheduled clockless mechanism to start operations on the presence of validity tokens only; iii) a design that avoids the need of temporary storage for tokens on the links of the DACs. Our preliminary tests on FPGA-based hardware show the feasibility of this approach.