The AMD 7800X3D and 7950X3D processors are powerful gaming CPUs, not because they have the most cores or the fastest clock speeds, but because they possess extremely rich cache resources. So, what exactly is CPU cache? Simply put, it’s a small block of ultra-high-speed memory integrated within the processor, specifically designed to enable the chip to efficiently fetch the data needed for computing. It’s like an instant acceleration warehouse custom-built for the CPU.
However, cache benefits aren’t limitless. The 7950X3D hasn’t blindly packed additional cache into every core, and there’s a reason behind this. While larger caches do enhance gaming performance to some extent, they also come with some drawbacks. To fully understand the intricacies of CPU cache and its comprehensive impact on performance, the following information is indispensable.
01
What is CPU cache?
The cache is a small block of memory built into the CPU. It can be integrated within a single processor core or shared across some or all of the cores. This memory is situated directly on the processor, close to the action, and crucial to ensuring that the CPU doesn’t need to fetch data from system RAM every time it executes a task. Different processors have varying cache capacities, ranging from a few kilobytes to several megabytes.
So, with high-speed SSDs and faster RAM available, why is cache still important? It all boils down to speed. As early as the 1990s, RAM speeds couldn’t keep up with CPU demands, posing a design challenge for CPUs. Smart designers introduced cache into the chip as a “close companion.”
Although cache has a much smaller capacity than RAM, it’s much faster, making up for this limitation. However, integrating memory into the compact chip is costly, so it’s typically not very large. AMD’s 3D V-Cache technology has broken through this limitation and successfully enhanced cache efficiency, resulting in the birth of a series of high-performance gaming chips. This clearly illustrates the benefits of technological advancement.
02
How does cache work?
With the increasing adoption of cache, its use alongside RAM has become more sophisticated, leading to the concept of a memory hierarchy: cache sits at the top, RAM is in the middle, and storage is at the bottom. This hierarchy keeps frequently used data close to the CPU, reducing wait times and making computers run more efficiently.
Cache itself is also tiered, mainly into L1, L2, and L3 levels. Although all are cache, each serves a distinct role.
The L1 cache is the first level closest to the CPU and is also the smallest. It consists of L1 instruction cache (L1i) and L1 data cache (L1d). Each CPU core has a dedicated L1 cache, typically only a few kilobytes, which stores recent or soon-to-be-used data. If the required data is not in L1, the CPU will move on to L2.
L2 cache is often dedicated to individual cores but can be shared across cores in some CPUs. It has much more capacity than L1. For example, each performance core of the Intel Core i9-12900K has 80KB of L1 cache and 1.25MB of L2 cache, the latter being almost 16 times larger than the former. However, as capacity increases, latency also grows, meaning it takes longer for the core to exchange information with L2. Given that CPUs must handle tasks quickly, this delay in L2 can’t be overlooked. If L2 also misses the target data, the CPU will turn to L3.
L3 cache is the big one, shared across cores and with a large capacity. For example, the 7950X3D has 128MB of L3 cache plus extra 3D V-Cache, while L2 is only 16MB. L3 has a higher latency than L2, but its crucial role is to reduce the CPU’s direct requests to RAM. RAM is slower and has higher latency than other memory levels, so every trip to RAM incurs an efficiency loss.
Some CPUs also have L4 cache, which usually acts as auxiliary RAM on the CPU package. For example, early Intel 14nm Broadwell CPUs had 128MB of embedded DRAM, while the subsequent Sapphire Rapids server CPUs could feature HBM2, which can be considered an extension of the cache hierarchy.
03
Is CPU cache important for gaming?
CPU cache has a significant impact on the gaming experience. While people traditionally believed that single-thread performance, instructions per cycle (IPC), and clock speed were the most critical factors in determining gaming performance, it now appears that cache size may be a key battleground in the competition between AMD and Intel.
The cache is especially crucial given modern game design. Games today are full of variables, frequently requiring the CPU to handle simple instruction sets. If the cache isn’t sufficient, the GPU is left “waiting” for the CPU, as bottlenecked instructions slow down overall speed. AMD’s 3D V-Cache technology provides significant improvements in this regard, which is evident in gaming CPU performance comparison charts where you can see a clear difference.
In recent years, games have increasingly relied on cache. AMD recognized this early on, consistently increasing cache capacity in its CPUs. It further expanded this advantage through its 3D V-Cache technology in the Ryzen 7 5800X3D and the subsequent Ryzen 7000 series.
Intel has also stepped up, equipping its latest CPU series with the most cache ever to ensure competitive gaming performance with AMD. As cache sizes continue to grow, the limits of gaming performance will keep being pushed forward.
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