I am trying to compare the Pros and Cons for the implemetation of FFT using DSP or FPGA. For DSP, I would like to us TI's chip; For FPGA I would like to use Xilinx's chip. I think both of them are able to complete a 128 pt or 256 pt fix point FFT. What I don't know are the price, speed and any other concern.

A:

An n-point FFT requires something on the order of n*log(n) multiplies and adds. Figure that the TI chip is going to require something on the order of 5-20 clock ticks * n * log_2(n) to get it done. An FPGA will do whatever you design it for, with a _BIG_ tradeoff between speed, logic utilization, and engineering time -- e.g. with a big enough FPGA you could do an n-point FFT in log_2(n) steps, but it'd have to have 2n multipliers to do it.