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Open Access Thesis
Electrical & Computer Engineering
Master of Science (M.S.)
Year Degree Awarded
Month Degree Awarded
Many embedded applications implement block ciphers and sorting and searching algorithms which use multiple loop iterations for computation. These applications often demand low power operation. The power consumption of designs varies with the implementation choices made by designers. The sequential implementation of loop operations consumes minimal area, but latency and clock power are high. Alternatively, loop unrolling causes high glitch power. In this work, we propose a low area overhead approach for unrolling loop iterations that exhibits reduced glitch power. A latch based glitch filter is introduced that reduces the propagation of glitches from one iteration to next. We explore the optimal number of filters to be inserted for different applications that give a good balance between area and power. We also implement partial unrolling with glitch filters. This approach consumes less area while still giving energy savings comparable to the fully unrolled implementation.
Our approach is targeted to Xilinx and Altera FPGAs. We simulate different implementation choices and compare energy results to evaluate the savings. We demonstrate our approach on SIMON-128 and AES-256 block ciphers and a sorting algorithm. We prototype our design on Xilinx Artix-7 and Altera Cyclone-IV-GX FPGA development boards and measure the actual power savings. Results show up-to 90% dynamic energy reduction in Xilinx designs, and 97% reduction in Altera designs with our glitch filtering approach due to glitch power reduction.
Dumpala, Naveen Kumar, "Energy Efficient Loop Unrolling for Low-Cost FPGAs" (2017). Masters Theses. 576.