THE CRUNCH
An engineering sample of the never-released Ryzen 9 5900X3D has appeared on the Chinese Chiphell forums, according to Tom's Hardware. The 12-core Zen 3 chip shows 128MB of L3 cache, double the standard Ryzen 9 5900X, achieved by stacking 64MB of 3D V-Cache onto one of its two Core Complex Dies, the two chiplets that make up the processor. AMD teased a 12-core 3D V-Cache prototype at Computex 2021 but never shipped one, instead launching the eight-core Ryzen 7 5800X3D, which remains a strong gaming CPU on the AM4 platform four years on.
The chip was no total secret. At Computex 2021 AMD showed a "12-core 3D Chiplet Prototype" that beat a regular Ryzen 9 5900X by up to 15% in average gaming performance, with both chips pinned at 4 GHz. The engineering sample carries the identifier 100-000000652-20_48/32_Y and shows a 4,649 MHz clock speed, which Tom's Hardware reads as a likely boost clock, roughly 100 MHz below the standard 5900X's 4.8 GHz.
The 128MB layout was only one experiment. Gamers Nexus, during a visit to AMD's labs, captured 12-core and 16-core Zen 3 chips with 192MB of L3, meaning 64MB of 3D V-Cache stacked on both CCDs. Specifications for these prototypes remain unconfirmed by AMD.
Tom's Hardware argues AMD's eventual choice of an eight-core, single-CCD design was the right call for gaming: stacking cache on both dies brings cross-die latency and lower clocks from thermal and power limits, which helps productivity but not games. The company points to its own CPU hierarchy, where the 12-core Ryzen 9 9900X3D trails the 8-core Ryzen 7 9800X3D in gaming. AMD did later bring 3D V-Cache to its bigger chips on Zen 4 and beyond, with the Ryzen 9 7900X3D, 7950X3D, 9900X3D and 9950X3D.