Alongside sparse RDNA 4 graphics card particulars and considerably denser cell chip bulletins, AMD additionally introduced the Ryzen 9 9950X3D and 9900X3D this CES 2025. Much like their 7000-series counterparts, nonetheless, and regardless of every CPU having two Core Complex Dies (CCDs) filled with CPU cores, solely one of many two CCDs has 3D V-Cache stacked beneath or on high (beneath for 9000X3D chips and on high for 7000X3D ones).
This, nonetheless, does not appear to be attributable to any technical limitations, however simply because it isn’t value it. HardwareLuxx says it requested AMD about it and “the reply was stunning: there aren’t any technical causes or challenges” why “we’ve not seen a Ryzen processor with two CCDs and 3D V-Cache on every of the CCDs.”
Apparently, “such a processor would merely be too costly and video games wouldn’t profit from a second CCD with 3D V-Cache to the identical extent because the step from 32 to 96 MB L3 cache for one CCD.”
The AMD Ryzen 7 9800X3D, the present finest CPU for gaming, has only one CCD and 64 MB of 3D V-Cache that sits beneath it. This 3D-stacked cache is nice for gaming, which could be very cache-consumptive.
The just-announced Ryzen 9 9900X3D and 9950X3D, nonetheless, have two CCDs—the previous with six cores per CCD and the latter with 8 cores per CCD. But the 3D V-Cache sits beneath simply one in every of these chiplets, which implies the top-end 9950X3D has the identical 64 MB of 3D V-Cache because the 9800X3D, and solely 8 of its cores (once more, just like the 9800X3D) entry it.
The good thing about that is twofold. First, the cores on the CCD with out the chiplet can enhance to a better clock pace. Second, there are extra cores, which is nice for functions that require plenty of multicore efficiency. Crucially, with the 9950X3D a minimum of, along with these two advantages, we also needs to get comparable gaming efficiency to the 9800X3D, given it nonetheless has eight cores with entry to 64 MB of 3D V-Cache.
That’s the idea, anyway. In observe, efficiency will depend upon how nicely software program handles choosing between cores with entry to 3D V-Cache and sooner cores that lack such entry. CPU core scheduling could cause points, which was famous with the 7900X3D and 7950X3D.
One may naturally suppose the subsequent step can be to chuck stacked cache beneath each chiplets. However, as AMD factors out to HardwareLuxx, there’s little profit to doing in order it is “too costly and video games wouldn’t profit.”
That’s primarily as a result of thread schedulers attempt to maintain all recreation threads operating on the cores of a single CCD regardless. And inter-CCD latency is so excessive that it might make no sense for these cores to succeed in throughout to the opposite chiplet’s stacked cache. As AMD reportedly says, video games would not profit.
Which is not to say that nothing would profit. As HardwareLuxx factors out, “there are functions that might undoubtedly profit from 192 MB of L3 cache with 16 cores.” But a recreation will not be one in every of them, and AMD has clearly—till now, a minimum of—judged that the marketplace for these functions which may profit is not sufficiently big to economically justify making dual-stacked X3D chips.
