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UBC Theses and Dissertations

Modeling and reduction of dynamic power in field-programmable gate arrays Lamoureux, Julien

Abstract

Field-Programmable Gate Arrays (FPGAs) are one of the most popular platforms for implementing digital circuits. Their main advantages include the ability to be (re)programmed in the field, a shorter time-to-market, and lower non-recurring engineering costs. This programmability, however, is afforded through a significant amount of additional circuitry, which makes FPGAs significantly slower and less power-efficient compared to Application Specific Integrated Circuits (ASICs). This thesis investigates three aspects of low-power FPGA design: switching activity estimation, switching activity minimization, and low-power FPGA clock network design. In our investigation of switching activity estimation, we compare new and existing techniques to determine which are most appropriate in the context of FPGAs. Specifically, we compare how each technique affects the accuracy of FPGA power models and the ability of power-aware CAD tools to minimize power. We then present a new publicly available activity estimation tool called ACE-2.0 that incorporates the most appropriate techniques. Using activities estimated byACE-2.0, power estimates and power savings were both within 1% of results obtained using simulated activities. Moreover, the new tool was 69 and 7.2 times faster than circuit simulation for combinational and sequential circuits, respectively. In our investigation of switching activity minimization, we propose a technique for reducing power in FPGAs by minimizing unnecessary transitions called glitches. The technique involves adding programmable delay elements at inputs of the logic elements of the FPGA to align the arrival times, thereby preventing new glitches from being generated. On average, the proposed technique eliminates 87% of the glitching, which reduces overall FPGA power by17%. The added circuitry increases the overall FPGA area by 6% and critical-path delay by less than 1%. Finally, in our investigation of low-power FPGA clock networks, we examine the tradeoff between the power consumption of FPGA clock networks and the cost of the constraints they impose on FPGA CAD tools. Specifically, we present a parameterized framework for describing FPGA clock networks, we describe new clock-aware placement techniques, and we perform an empirical study to examine how the clock network parameters affect the overall power consumption of FPGAs. The results show that the techniques used to produce a legal placement can have a significant influence on power and delay. On average, circuits placed using the most effective techniques dissipate 9.9% less energy and were 2.4% faster than circuits placed using the least effective techniques. Moreover, the results show that the architecture of the clock network is also important. On average, FPGAs with an efficient clock network were up to12.5% more energy efficient and 7.2% faster than other FPGAs.

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License

Attribution-NonCommercial-NoDerivatives 4.0 International

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