We've seen several rumors on this already, but this time the rumor solidified as AMD really is pursuing a BIG.Little architecture for future generatioN ZEN-based processors. Big are performance cores, little cores, energy-friendly ones. 

Intel is already moving to such a processor architecture this year with the next-gen core processors, AMD also is and has been working on design plans as it now is confirmed. The Big.little design would make an introduction in their Zen 4 but more likely Zen 5 series. The patent is names 'Method of task transition between heterogeneous processors', and was filed back in December of 2019 already. It illustrates that the large and small cores are processed in separate core complexes so that tasks can be distributed more efficiently.

A timer in the small core core-complex keeps track of how long processes run at the highest achievable clock speed by the small cores. After a certain time, the still-active processes are moved to the large cores, in order to process them faster there. In addition, the small cores are intended to be as economical as possible, processing intensive tasks on the small cores is therefore not in line with the intended use.

The same is correct for the large cores, although in this case tasks are moved to the small cores when the maximum achievable performance is not needed. After all, this means that they can be processed on the small cores with lower consumption.

It'll be a while, even a long time before we'll see AMD make this move and introduced such processors to the market. Zen 5 will probably not be uncovered until the year 2023.

Patent Again confirms AMD pursuing BIG.Little architecture