Native Double Precision LINPACK Implementation on a Hybrid Reconfigurable CPU

Applications requiring double precision (DP) arithmetic executed on embedded CPUs without native DP support suffer from prohibitively low performance and power efficiency. Hybrid reconfigurable CPUs, allowing for reconfiguration of the instruction set at runtime, appear as a viable computing platform for applications requiring instructions not supported by existing fixed architectures. Our experiments on a Stretch S6 as prototypical platform show that limited reconfigurable resources on such architectures are sufficient for providing native support of DP arithmetic. Our design using a DP fused multiply-accumulate (FMA) extension instruction achieves a peak performance of 200 MFlop/s and a sustained performance of 22.7 MFlop/s at a clock frequency of 100 MHz. It outperforms LINPACK using software-emulated DP floating-point arithmetic on the S6 by a factor of 5.7 while achieving slightly higher numerical accuracy. In single precision, multiple floating-point operators can be implemented in parallel on the S6.