Zen (microarchitecture)

Zen is the codename for a family of computer processor microarchitectures from AMD, first launched in February 2017 with the first generation of its Ryzen CPUs.
History.
First generation.
The first generation Zen was launched with the Ryzen 1000 series of CPUs (codenamed Summit Ridge) in February 2017. The first Zen-based preview system was demonstrated at E3 2016, and first substantially detailed at an event hosted a block away from the Intel Developer Forum 2016. The first Zen-based CPUs reached the market in early March 2017, and Zen-derived Epyc server processors (codenamed "Naples") launched in June 2017 and Zen-based APUs (codenamed "Raven Ridge") arrived in November 2017. This first iteration of Zen utilized Global Foundries' 14nm manufacturing process.
Second generation.
Zen+ was first released in April 2018, powering the second generation of Ryzen processors, known as Ryzen 2000 (codenamed "Pinnacle Ridge") for mainstream desktop systems, and Threadripper 2000 (codenamed "Colfax") for high-end desktop setups. This generation used Global Foundries' 12nm process, an enhanced version of their 14nm node.
Third generation.
The Ryzen 3000 series CPUs were released on July 7, 2019, while the Zen 2-based Epyc server CPUs (codename "Rome") were released on August 7, 2019. Zen 2 also powered a line of desktop APUs marketed as Ryzen 4000. These were the first consumer CPUs using TSMC's 7nm process node. Zen 2 introduced the chiplet based architecture, where all desktop, workstation and server CPUs utilized the same core chiplets. The IO for these processors was taken care of by an IO die, separate from the processing cores. The IO die used by Matisse processors was a small chip on GF 12nm, where as the IO die utilized for Threadripper and Epyc was much larger, able to handle more IO. These chiplets were linked by AMD's own second generation Infinity Fabric, allowing a low-latency interconnect between the cores and their IO. Matisse was limited to two 8-core chiplets and Threadripper/Epyc was limited to eight 8-core chiplets. The processing cores in the chiplets were organized in CCXs (Core Complexes) of four cores, linked together to form a single eight core CCD (Core Chiplet Die).
Fourth generation.
Zen 3 was released on November 5, 2020, using a more matured 7nm manufacturing process, powering Ryzen 5000 series CPUs & APU's (codename "Vermeer" (CPU) and "Cézanne" (APU)) and Epyc processors (codename "Milan"). Zen 3's main performance gain over Zen 2 is the introduction of a unified CCX, which means that each core chiplet is now composed of eight cores with access to 32MB of cache, instead of two sets of four cores with access to 16MB of cache each.