Cache is not something PC gamers think about enough. At least, that seems to be AMD’s thinking lately.
With the release of 3D V-Cache on the Ryzen 7 5800X3D, AMD has just proven its point. The 5800X3D is the most powerful gaming CPU you can buy, and 3D V-Cache is to thank. But a question arises: Why?
Cache has always been important, but AMD didn’t decide to apply its 3D Hybrid Bond package to cache on mere hunch. After finishing my review of the Ryzen 7 5800X3D, I sat down with Robert Hallock, Director of Technical Marketing at AMD, to understand what cache does in games, why it’s important, and why gaming was the perfect design goal. for the most unique processor of 2022.
What is the cache?
Before we talk about anything else, we need to talk about cache – specifically, what the CPU cache does in the world when you’re playing games. A cache is pretty simple: it’s a bit of super-fast memory on your CPU that can hold instructions. Hallock explained the importance of cache this way: “The more local instructions you can keep on the processor, the less time you’ll spend fetching them elsewhere.”
Time (or more accurately latency) is what Hallock calls the “great governor of performance.” Your average frame rate is just an abstraction of latency, an easier-to-understand shortcut than the time it takes to render each frame. That’s the point.
It’s the hardware industry’s “great quest,” according to Hallock, to hide or remove latency to improve performance.
The CPU cache contains instructions that govern what your other components do, and in games these instructions can change a lot. Randomness is what causes latency, as your CPU has to send instructions to the GPU to fetch a texture or character model (among dozens of other things).
More cache means the CPU doesn’t need to fetch data from your system’s RAM, which could increase latency by 10 times or more.
That doesn’t mean more cache is inherently better for gaming. Much depends on the game, but more importantly, when the game was created.
three buckets
When it comes to defining design goals for a CPU like the Ryzen 7 5800X3D, Hallock says games fall into three main categories:
- Frequency Sensitive — League of Legends, Civilization VI
- Latency Sensitive — Fortnite, Forza Horizon 4
- GPU sensitive — Dying Light 2, Red Dead Redemption 2
Games are very demanding today, so the buckets above aren’t perfect. A game like Assassin’s Creed Valhalla is concerned with GPU, latency, and frequency, but is more limited by the power of your GPU, so it won’t benefit as much from V-Cache 3D. You can see it from some of my tests in the table below.
Hallock was careful not to make sweeping statements, as what a game is responsive to “doesn’t quite fit the genre”. The most important indicator is the age of the game. Hallock highlighted older titles like Counter-Strike: Global Offensive and Grand Theft Auto V as examples of older games which are generally more frequency sensitive. Newer games like far cry 6 and Infinite Halo will generally see a greater benefit from more cache.
You can see that in the chart below, with the Ryzen 7 5800X3D delivering a significant performance boost over even the Ryzen 9 5950X in Far cry 6.
The game’s application programming interface (API) is also a huge influencer. Games from the DirectX 9 era are generally more frequency sensitive, while newer DirectX 11 and DirectX 12 games make better use of cache. And APIs like Vulkan can make a huge difference. hallock pointed out Dota 2 for example: “Following its API change to Vulkan, [Dota 2] is heavily influenced by cache performance.
Ultimately, however, the advantage of something like 3D V-Cache largely comes down to the type of games that are popular today. Newer APIs are better equipped to take advantage of things like 3D V-Cache, but it’s player randomness that takes advantage of this. Multiplayer titles like Apex Legends are a good example here, where you might have “a chance encounter with an enemy or moving from place to place because a firefight has just broken out”.
“It’s the kind of player behavior that makes a computer change its mind,” says Hallock. As randomness becomes more ingrained in the games we play, the role of cache is to move instructions to the right place to keep latency as low as possible.
It’s also not an idea out of left field. Looking at the Ryzen 5000 processors, even the Ryzen 5 5600X sports 2MB more L3 cache than Intel’s Core i9-12900K. Different architectures handle caching, well, differently, but clearly AMD has this specification in mind. Consider that the $300 Ryzen 5 5600X comes close to Intel’s gaming flagship, despite costing less than half the price and featuring 10 fewer cores.
Post frequency
There’s a big elephant in the room with the Ryzen 7 5800X3D: Frequency. It’s 200 MHz slower than the Ryzen 7 5800X, and you can’t overclock it without some serious workarounds. But Hallock says we’re entering an age where frequency is less important, at least in the meantime.
“The whole industry has been hovering around 5 GHz for some time. And we recognize it. This idea of exploring interesting packaging technologies is an effort to end this impasse. »
Frequency is important, and Hallock says it sits alongside packaging and process as a powerful tool in the toolbox. Yet it is true that we see less benefit with increased frequency. Look to the Core i9-12900KS as a prime example, where even a 300MHz boost offers little to no benefit in games.
“Will a few hundred extra megahertz make a difference here? And I think you see indicators everywhere. The answer is no, unlikely.
Overclocking is another matter, a case of compromise given that many modern titles don’t scale to frequency the same way older games do. It comes down to voltage and thermals, with the parts not offering enough headroom for easy and safe overclocking. Hallock says AMD “felt it would be kind of wrong not to” anyway.
It’s a compromise that Hallock acknowledges, and over time he says that AMD “will continue to push that limit” and that the company intends to bring benefits such as overclocking to chips stacked in 3D with future releases.
Looking forward
The Ryzen 7 5800X3D is a remarkable chip, designed from the ground up for the games we play today instead of the endless IPC (instructions per clock) hunt that has been going on for 30 years. And 3D V-Cache is just the first application of AMD’s 3D Hybrid Bond technology, which allows AMD to consider placing different modules on the same chip.
It’s an interesting product, but it’s also a pulse-pounding read on what’s important to PC gaming today. Hallock says this might help people pause and look at what a high-performance gaming PC will look like in the future, because based on the performance of the Ryzen 7 5800X3D, it’s starting to look quite different.
This article is part of ReSpec – an ongoing bi-weekly column that features in-depth discussions, tips and reports on the technology behind PC gaming.
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