Long FPGA CAD runtime has emerged as a limitation to the future scaling of FPGA densities. Already, compile times on the order of a day are common, and the situation will only get worse as FPGAs get larger. Without a concerted effort to reduce compile times, further scaling of FPGAs will eventually become impractical. Previous works have presented fast CAD tools that tradeoff quality of result for compile time. In this paper, we take a different but complementary approach. We show that the

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... tecture of the FPGA itself can be designed to be amenable to fast-compile. If not done carefully, this can lead to lower-quality mapping results, so a careful tradeoff between area, delay, power, and compile run-time is essential. We investigate the extent to which run-time can be reduced by employing high-capacity logic blocks. We extend previous studies on logic block architectures by quantifying the area, delay and CAD runtime trade-offs for large capacity blocks, and also investigate some multi-level logic block architectures. In addition, we present an analytically derived equation to guide the design of logic block I/O requirements.