One of the big announcements at CES for us PC gaming freaks was AMD’s new Ryzen 7000 series CPUs with added 3D V-Cache (opens in new tab). It’s not the first time AMD has crammed in some extra cache memory to boost gaming performance. But AMD is doing things differently this time and with the new approach comes both pros and cons.
The most obvious difference is that AMD offers a choice of three X3D models, the Ryzen 9 7950X3D, the Ryzen 9 7900X3D and the Ryzen 7 7800X3D. Last time it was only the lonely one Ryzen 7 5800X3D (opens in new tab).
Along with that greater choice comes more options in terms of core counts. Instead of a single eight-core model, you can now also opt for 16 cores or 12 cores with your tasty chunk of 3D V-Cache.
Except it’s not that simple. While the eight-core model is essentially the same as the previous 5000 series chip, featuring a single eight-core core complex die (CCD) with added V-Cache, the 12 and 16 core models are dual CCD.
And it turns out those CCDs are not equal. Where two CCDs are used in these new X3D chips, only one of them gets the added V-Cache. The net result is a rather complex asymmetrical design that raises all sorts of questions.
That said, the asymmetrical layout at least explains why the 7800X3D is so much slower than the other two models. The eight-core chip has a maximum boost speed of 5 GHz, much lower than the 5.7 GHz and 5.6 GHz speeds of the 16-core and 12-core models.
This is because the V-Cache limits the boost rate of any CCD it is applied to. The 7800X3D has one CCD, so it’s limited to that clock speed with V-Cache limit. However, the other two chips can boost their non-V-Cache enhanced CCDs to the same clock speeds as their conventional Ryzen 7000 series counterparts, at 5.7 GHz and 5.6 GHz respectively.
That immediately poses a problem. How do you ensure that a certain application or game runs on the right one with two very different CCDs? Indeed, which is the correct one?
With the old Ryzen 7 5800X3D, the clock speed on paper was only a few hundred MHz lower than the standard chip. The benefit of the 3D V-Cache far exceeded that. But here up to 700 MHz is quite a big gap. At what point does clock speed trump V-Cache, and in which games?
Of course, CPUs rarely run at their maximum boost speeds in gaming terms. And it remains to be seen how big that real-world clock speed difference will be.
Perhaps the more pertinent question is whether some games prefer the cache or the clocks. What we do know is that AMD makes that assumption – that it will vary by game.
AMD told our sister site, Tom’s hardware (opens in new tab)that it is working with Microsoft on an update to the Windows operating system that will be paired with a new chipset driver to identify and schedule workload per game to ensure the optimal CCD is prioritized for a given game.
Those that benefit most from the V-Cache will run on the relevant CCD, while those that run faster due to higher clocks will instead be redirected to the faster non-V-Cache CCD.
It’s worth remembering that Intel is doing something similar with its own asymmetric CPUs, which feature two very different core architectures in a single chip. Indeed, the performance and technical gap between Intel’s P Cores and E Cores is arguably much larger than AMD’s V-Cache and non-V-Cache CCDs.
Of course, Intel has more technical resources than AMD. So, the fact that Intel managed to make its hybrid CPU design work so well does not guarantee that AMD will be able to make its new asymmetric chips work optimally.
The advantage of AMD’s new approach is that you have the best of both worlds in one chip. Assuming a game is scheduled on the correct CCD, you have both a high clocked option and a V-Cache option. Stick it on the correct CCD and you have the best possible performance.
But the new approach does add complexity. And it means trusting AMD to have done the job with a given game. In an ideal world, hardware that just works with any software and doesn’t require manual tuning is preferable.
In practice, it’s probably safe to assume that AMD will have the job done with any major existing or new game release. It’s probably just edge cases with lesser-known games and apps where the optimization work may not have been done.
Oh, and one other question remains unanswered, albeit only for one of the new CPU models. We know that the eight-core chip is pure V-Cache, and the 16-core model has one full eight-core V-Cache CCD and one full eight-core non-V-Cache chip. But what about the Ryzen 9 7900X3D?
That’s a 12-core chip. So, does it have two six Core CCDs? Or maybe an eight-core V-Cache CCD and a four-core non-V-Cache CCD? And of those two options, which one might be the best choice for gaming?
Some games may run faster on eight V-Cache cores than six. Indeed, others may run best on eight highly clocked cores than six or even just four. Of all the new X3D CPUs, that 12-core model seems to be the most problematic.
We suspect that for gamers, the simplest and most cost-effective option is the straight eight-core all V-Cache 7800X3D. For now, AMD has not compared that chip directly to the higher-core-count models in its own internal benchmarks. So we are curious if there are games where the 16-core option is actually faster.