Heterogeneous processors such as ARM's big.LITTLE have become popular for embedded systems. They o er a choice between running workloads on a high performance core or a low-energy core leading to increased energy e ciency. However, the core con gurations are xed at design time which o ers a limited amount of adaptation. Dynamic Multicore Processors (DMPs) bridge the gap between homogeneous and fully recon gurable systems. Cores can fuse dynamically to adapt the computational resources to the needs of di erent workloads. There exists multiple examples of DMPs in the literature, yet the focus has mainly been on static partitioning. This paper conducts the rst thorough study of the potential for dynamic recon guration of DMPs at runtime. We study how performance varies with static partitioning and what software optimizations are required to achieve high performance. We show that energy consumption is reduced considerably when adapting the number of cores to program phases, and introduce a simple online model which predicts the optimal number of cores to use to minimize energy consumption while maintaining high performance. Using the San Diego Vision Benchmark Suite as a use case, the dynamic scheme leads to ∼ 40% energy savings on average without decreasing performance.