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arXiv · 1908.09930

Cyclic Sequence Generators as Program Counters for High-Speed FPGA-based Processors

P. A. Suggate·R. W. Ward·T. C. A. Molteno
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Abstract

This paper compares the performance of conventional radix-2 program counters with program counters based on Feedback Shift Registers (FSRs), a class of cyclic sequence generator. FSR counters have constant time scaling with bit-width, $N$, whereas FPGA-based radix-2 counters typically have $O(N)$ time-complexity due to the carry-chain. Program counter performance is measured by synthesis of standalone counter circuits, as well as synthesis of three FPGA-based processor designs modified to incorporate FSR program counters. Hybrid counters, combining both an FSR and a radix-2 counter, are presented as a solution to the potential cache-coherency issues of FSR program counters. Results show that high-speed processor designs benefit more from FSR program counters, allowing both greater operating frequency and the use of fewer logic resources.

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P. A. Suggate, R. W. Ward, T. C. A. Molteno. 2019-08-26. Cyclic Sequence Generators as Program Counters for High-Speed FPGA-based Processors. https://arxiv.org/abs/1908.09930

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