Improving bitstream compression by modifying FPGA architecture

The size of configuration bitstreams of field-programmable gate arrays (FPGA) is increasing rapidly. Compression techniques are used to decrease the size of bitstreams. In this paper, an appropriate bitstream format and variable symbol lengths are proposed to utilize the routing patterns for enhancing the compression efficiency. An order of inputs of multiplexers in switch modules is also proposed to improve the symbol statistics and hence, the compression efficiency. A framework to generate the bitstream and hardware description of FPGAs is developed as well. Experimental results over 20 MCNC benchmarks show that by applying the proposed approaches, the compression rate is improved by 46% on average compared to the methods with fixed symbol lengths without any area and performance degradation.