Configurable Multimode Embedded Floating-Point Units for FPGAs

Performance of field-programmable gate arrays (FPGAs) used for floating-point applications is poor due to the complexity of floating-point arithmetic. Implementing floating-point units (FPUs) on FPGAs consume a large amount of resources. This makes FPGAs less attractive for use in floating-point intensive applications. Therefore, there is a need for embedded FPUs in FPGAs. However, if unutilized, embedded FPUs waste space on the FPGA die. To overcome this issue, we propose a flexible multimode embedded FPU for FPGAs that can be configured to perform a wide range of operations. The floating-point adder and multiplier in our embedded FPU can each be configured to perform one double-precision operation or two single-precision operations in parallel. To increase flexibility further, access to the large integer multiplier, adder and shifters in the FPU is provided. Benchmark circuits were implemented on both a standard Xilinx Virtex-II FPGA and on our FPGA with embedded FPU blocks. The results using our embedded FPUs showed a mean area improvement of 5.5 times and a mean delay improvement of 5.8 times for the double-precision benchmarks, and a mean area improvement of 3.8 times and a mean delay improvement of 4.2 times for the single-precision benchmarks. The embedded FPUs were also shown to provide significant area and delay benefits for fixed-point and integer circuits.