They both use the same kind of components; the FPGA does not have a speed advantage, you are simply comparing the speed of a very simple circuit element to the

They both use the same kind of components; the FPGA does not have a speed advantage, you are simply comparing the speed of a very simple circuit element to the speed of a very complicated pipeline. You would use an FPGA to simulate a special purpose circuit, which would be faster than a CPU for its specific purpose. We have CPUs because having a general purpose processing chip is incredibly handy when you want to be able to do more than one thing. EDIT: I forgot to mention that the device outputs in one clock cycle by definition: if your clock is too fast then your components output signals dont have time to stabilize and you will get read errors, so you ensure your clock is slow enough for everything to stabilize.