Accuracy-Performance Tradeoffs on an FPGA through Overclocking

Embedded applications can often demand stringent latency requirements. While high degrees of parallelism within custom FPGA-based accelerators may help to some extent, it may also be necessary to limit the precision used in the datapath to boost the operating frequency of the implementation. However, by reducing the precision, the engineer introduces quantization error into the design. In this paper, we demonstrate that for many applications it would be preferable to simply overclock the design and accept that timing violations may arise. Since the errors introduced by timing violations occur rarely, they will cause less noise than quantization errors. Through the use of analytical models and empirical results on a Xilinx Virtex-6 FPGA, we show that a geometric mean reduction of 67.9% to 98.8% in error expectation or a geometric mean improvement of 3.1% to 27.6% in operating frequency can be obtained using this alternative design methodology.