Programmable and configurable processors are becoming increasingly popular for embedded wearable devices. In configurable processors technology it is a common practice to define specialized instructions in order to boost the performance of the device. These instructions may not fit in a single clock period and therefore, may require two clock periods for completion of a given task. In the past, we have proposed a method to generate a clock where each cycle can have a different length, and in this paper we will investigate the performance gain it can give compared to standard clocking. Using our variable fractional clock period method, a gain of more than 10% in performance is easily obtained, with a maximum of 21%, compared to current best clocking techniques used in extensible configurable processors. We also show that the overall speedup of our method follows the well known Amdahl?s law, but without quantization of the acceleration factor.