A72 vs A53 processor core

ARM has divided its A-series core into three categories- high performance core, high efficiency core, ultra-efficiency core

A53 lies in the middle, i.e., it belongs to the ‘high efficiency core’ group. Whereas, A72 sits at the top, i.e., it belongs to high performance group. A53 is an efficiency- focused core, i.e., it prioritises performance per watt, whereas A72 is a performance core, i.e., it prioritises performance ( yeah, definitely within the given thermal budget).

Let’s look into their differences:

• A72 is a performance oriented core: A72 is a big core having more L1 and L2 cache, more complex circuitry.
• OoO execution: A72 core supports out-of-order execution (requires complicated circuit and logic & therfore takes more die space & is expensive, moreover it is always turned 'on' so uses more power but gives you more performance) whereas A53 core do not support it (less performance).
• pipeline length or depth: A72 has 15 stages pipeline whereas A53 implements 8 stages pipeline. So, A72 will have, virtually, 15 instruction at the same time in different stages all the time, whereas, A53 will be having only 8 instruction. Accordingly, A72 will be the first to finish executing instructions.
• Branch predictor: A72 has more complicated and sophisticated branch predictor as compared to A53 core. This will bring higher cache hit and so higher performance.

As you can see A53 provide good performance per Ghz (if it is not clocked too high as cores tend to give diminishing performance returns with every increase in clock speed and gobble up more & more power) and takes up less space than A72 on silicon wafer.

 A72 core will give more performance regardless if it is clocked lower than A53 or the same as A53 but will use more power even if it is clocked lower than A53 core (unless the code is optimised for A72 microarchitecture, E.g., things like code is heavily branched, optimised for pipelining or Ooo execution in that case A72 will use less power).

Summary: A72 core is part of A72 microarchitecture (performance-oriented), Whereas, A53 core is part of A53 microarchitecture (efficiency focused).

To get both performance and higher battery you should consider buying a SOC which has both A53 and A72 core.