The Cortex-A53 is certainly a respectable processor within its design constraints. It is from 2012, and I think it is either the smallest or the second-smallest

The Cortex-A53 is certainly a respectable processor within its design constraints. It is from 2012, and I think it is either the smallest or the second-smallest implementation of AArch64 that Arm have designed. It is very power-efficient, and that was the design goal. You definitely can make an SoC that only has “efficiency” cores, and it can even run Android, but putting it in a smartphone indicates that pure manufacturing cost is your only design consideration.