Heterogenous multicore architectures are becoming ubiquitous in high-end smartphones. In this paper, we present a study of two modern heterogeneous multicore architectures based on real measurements. One architecture implements the well-established ARM big.LITTLE 2-cluster approach while the second one takes a leap forward and extends the concept to 3 clusters. In concrete, we analyze the performance of those platforms running parallel workloads. Furthermore, we study the energy and power consumption of the 3-cluster architecture and the effects of high clock frequency on SoC temperature.