In the 1st section are briefly introduced the basic IFP classes, emphasising their common and distinctive characteristics. Here, are also pointed out that the evolution of pipeline, VLIW and superscalar processors inevitably had to happen in that order. Next, in the 2nd section are overviewed the constraints, which are imposed on the parallel execution of instructions, if a sequential consistency is required. These constraints are the data, control and resource dependences, which are common to all IFP classes and can, therefore, be discussed jointly. Finally, in the 3rd section we are going to investigate how much speed-up potential functional parallelism has, which is to be utilised by all kinds of IFP process ors.