While there are some exceptions, in general an 8 core ARM based processor uses a system known as Heterogeneous Multi-Processing (HMP) which means that not all the cores are equal (hence Heterogeneous). In a modern 64-bit processor this would mean that a cluster of Cortex-A57 or Cortex-A72 cores would be used in conjunction with a cluster of Cortex-A53 cores. The A72 is a high performance core, while the A53 has greater energy efficiency. This arrangement is known as big.LITTLE