A unique engineering sample of the AMD Ryzen 9 5900X3D processor appeared on the Chinese Chiphell forum, but the sample was never mass-produced. This 12-core, 24-thread Zen 3 architecture chip numbered 100-000000652 reveals a very interesting detail: AMD engineers had already begun experimenting with an asymmetric cache layout before the introduction of the AM5 socket.
The found instance received a total of 128 MB of L3 cache. An additional 64 MB 3D V cache layer is installed on one of the two six-core CCD dies (identical to the 7900X3D and 9900X3D).
Resurrecting the “stone” proved difficult. The latest BIOS version categorically refuses to boot, so the system can only be booted with the help of older motherboard firmware with microcode SMU 56.70.0. Owners of this unusual chip have contacted ASRock support to request that compatibility with this unique chip be restored in a future update.
