A CAD framework for Malibu: an FPGA with time-multiplexed coarse-grained elements

Modern FPGAs are used to implement a wide range of circuits, many of which have coarse-grained and fine-grained components. The ever-increasing size of these circuits places great demand on CAD tools to synthesize circuits faster and without loss in quality. Synthesizing coarse-grained components onto fine-grained FPGA resources is inefficient, and past attempts to optimize FPGAs for word-oriented datapaths have met with limited success. This paper presents a CAD flow to fully compile Verilog into a configuration bitstream for a new type of FPGA with time-multiplexed coarse-grained resources. We demonstrate two approaches with gains of 61x and 42x in synthesis time on average compared to QuartusII, but due to time-multiplexing and current synthesis limitations we achieve circuit speeds of 14x and 8.5x slower on average. We show the tools can also trade density for maximum clock frequency.

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