Architecture-Specific Packing For Virtex-5 Fpgas

We consider packing in the commercial FPGA context and examine the speed, performance and power trade-offs associated with packing in a state-of-the art FPGA - the Xilinx (R) Virtex (TM) -5 FPGA. Two aspects of packing are discussed: 1) packing for general logic blocks, and 2) packing for large IP blocks. Virtex-5 logic blocks contain dual-output 6-input look-up-tables (LUTs). Such LUTs call implement any single logic function requiring no more than 6 inputs, or any two logic functions requiring no more than 5 distinct inputs. The second LUT Output is associated with slower speed, and therefore, must be used judiciously. We present placement-based techniques for dual-output LUT packing that; lead to improved area-efficiency and power, with minimal performance degradation. We then move on to address packing for large IP blocks, specifically, block RAMs and DSPs. We present a packing optimization that is widely applicable in DSP designs that leads to significantly improved design performance.