Unreleased AMD Ryzen 9 5900X3D Sample Surfaces With 128 MB of L3 Cache

A Chiphell forum user shared photos of an engineering sample of the unreleased AMD Ryzen 9 5900X3D, an AM4-era Zen 3 chip that appears to have been built for testing rather than retail. The sample has 24 threads, a 105 W TDP and a maximum clock speed of up to 4.85 GHz; monitoring tools reportedly showed it running at 4.65-4.73 GHz.

The unusual cache total comes from a 96 MB L3 cache on one chiplet and 32 MB on the other, meaning AMD added 3D V-Cache to only one of the processor's two core chiplets.

AMD previously showed Ryzen 9 5900X3D and 5950X3D prototypes with 3D V-Cache on both chiplets, for a total of 192 MB of L3 cache. By contrast, the single-chiplet design later appeared in the Ryzen 9 7950X3D and 9950X3D on the AM5 platform, while cache on both chiplets arrived this year with the Ryzen 9 9950X3D2 Dual Edition.

The sample's owner said it would not boot with the latest motherboard BIOS and displayed Q Code 90. It worked with an older BIOS using SMU firmware 56.70.0, and the owner contacted ASRock to ask about adding support to a newer BIOS. There has been no promise of support from AMD or ASRock, and engineering samples can require firmware that is not intended for retail processors.

AMD showed the 5900X3D and 5950X3D prototypes to journalists at its Austin labs in 2023. Those versions had cache on both chiplets and clock speeds of up to 4.4 GHz; the sample that has now surfaced has a different cache layout and higher reported clock speeds. Of the Zen 3 X3D lineup, only the eight-core Ryzen 7 5800X3D reached retail, launching in 2022. Why do you think AMD never released a Ryzen 5000 processor with this single-chiplet 3D V-Cache design and 128 MB of L3 cache?