AMD's new mobile Ryzen 4000 "Renoir" family — first teased at CES 2020 — has now been released. The 4000 mobile family marks a move from Zen+ to Zen2 cores, matching the 3000 desktop family. This is a significant development that accounts for a large portion of the generational performance and stamina changes.
https://www.notebookcheck.net/AMD-launches-the-Ryzen-4000U-series-and-claims-it-takes-the-ULV-performance-crown.457439.0.html