The 39000X comes packing AMD's Zen 2 microarchitecture spread across two small 7nm eight-core compute chiplets tied together with the Infinity Fabric interconnect via a larger 12nm I/O die (IOD). Each small 3900X compute chiplet, referred to as a CCD (Core Chiplet Die), comes with eight physical cores spread across two four-core Core Complexes (CCXes). Each CCX has 16MB of shared L3 cache, totaling 32MB of L3 cache per CCD, and 64MB of total cache for the entire chip. AMD disables two cores per CCD to create the 12-core 3900X.
Each 7nm CCD measures ~74mm2 and has 3.9 billion transistors, while the 12nm IOD is ~125mm2 and has 2.09 billion transistors. That means the 3900X comes with ~273mm2 of silicon that sports ~9.89 billion transistors.