Why does the Fast Fourier Transform core take so long to generate?
The length of the generation time is proportional to the size of the core. It has been observed that the larger point sizes, such as 32768 or 65536 points, take as long as two hours to generate. The smaller cores should not take so long.
Also, please note that a streaming architecture core will take longer to generate than a burst architecture core.
Please See (Xilinx Answer 29209) for a detailed list of LogiCORE Fast Fourier Transform (FFT) Release Notes and Known Issues.