GeneticFPGA is a Java-based tool for evolving digital circuits on Xilinx XC4000EXTM and XC4000XLTM devices. Unlike other FPGA architectures popular with Evolutionary Hardware researchers, the XC4000 series architectures cannot accept arbitrary configuration data. Only a small subset of configuration bit patterns will produce operational circuits; other configuration bit patterns produce circuits which are unreliable and may even permanently damage the FPGA device. GeneticFPGA uses novel software techniques to produce legal circuit configurations for these devices, permitting experimentation with evolvable hardware on the larger, faster, more mainstream devices. In addition, these techniques have led to methods for evolving circuits which are neither temperature, voltage, nor silicon dependent. An 8-bit counter and several digital frequency dividers have been successfully evolved using this approach. GeneticFPGA uses Xilinx's JBitsTM interface to control the generation of bitstream configuration data and the XHWIF portable hardware interface to communicate with a variety of commercially available FPGA-based hardware. GeneticFPGA, JBits, and XHWIF are currently being ported to the Xilinx VirtexTM family of devices, which will provide greatly increased reconfiguration speed and circuit density.