Next generation embedded systems will massively adopt on-chip manycore architectures to provide both performance and energy-efficiency. This trend will definitely establish the convergence of embedded computing and high-performance computing. In such a context, one major design challenge will concern the choice of adequate architecture parameters given system requirements. Moreover, it will affect the way applications can suitably exploit architecture resources for an efficient execution. This paper deals with manycore on-chip system design exploration by using via simulation. It presents an approach enabling one to study central design parameters in an accurate and cost-effective manner. This approach is illustrated through the design exploration for ARM big.LITTLE heterogeneous multicore technology in the gem5 framework.