When shopping for a new CPU, you're likely to come across many different CPU specifications, such as cores, clock speed, TDP, and manufacturing process. Another important aspect of CPU hardware is cache memory, which is responsible for speeding up CPU performance by storing frequently accessed data on the CPU itself.

CPU cache memory was developed to keep up with the demands of processors when they outpaced the speed of system memory (RAM) in the 1980s. Today's CPUs feature enormous amounts of cache memory compared to the early computers, and is a vital aspect of what makes modern computing tick. Let's understand the hierarchy of CPU cache memory and how it affects CPU performance.

What are the differences between L1, L2, and L3 cache?

Why do CPUs need all three?

Before the 1980s, CPU and RAM speeds were both low enough that the latter slowing down the former wasn't a huge concern. However, RAM speeds couldn't keep up with CPU speeds, and a new type of faster memory was needed. This is what led to the development of CPU cache memory. This onboard memory was way faster than system memory (around 10 to 100 times faster, in fact), and processors no longer had to wait for data to be fetched from the relatively slower RAM.

Now, CPU cache memory is not homogenous — it exists in three (occasionally four) variants, namely L1, L2, and L3. The primary differences between these three variants will come down to speed, capacity, and cost. While the L1 or primary cache sits closest to an individual CPU core, the L2 cache is found a bit farther away, with the L3 cache being the furthest from the core.

The L1 cache is the fastest but smallest memory buffer on a CPU core, typically measured in kilobytes. The L1 cache stores the data that your CPU is most likely to need when completing certain operations. Being around 100 times faster than the system memory, this is the first place your CPU looks at for fetching the data it needs. It's further divided into the instruction cache and the data cache. The instruction cache, as the name suggests, stores information about the operation that is to be performed, while the data cache stores the data on which the operation is to be performed.

Each CPU core has its own L2 cache memory, just like the L1 cache. Measured in megabytes on modern CPUs, the L2 cache is slower than the L1 cache, but still around 25 times faster than the system memory (RAM). The L2 cache is almost always larger than the L1 cache, usually around 6MB-12MB on most modern CPUs.

Finally, the L3 cache, or Last Level Cache, is the slowest but largest memory buffer available to the CPU (and still 10 times faster than RAM). Unlike the L1 and L2 cache, the L3 cache is shared between all the cores of the CPU. You'll typically see around 24MB-36MB of L3 cache on most modern CPUs, while AMD's Ryzen X3D processors can feature up to 128MB of 3D V-Cache (a form of L3 cache).

How does the CPU utilize various memory caches?

To cache or not to cache

The flow of data between the various forms of memory on your computer is as follows: primary storage, to system memory (RAM), to L3 cache, to L2 cache, to L1 cache. When the CPU needs to access data to perform a certain operation, it begins with the fastest memory it has available — the L1 cache. If it doesn't locate it in the L1 cache, it proceeds to the L2 cache, and then the L3 cache.

If the CPU finds the requisite data in any of the three caches, this is termed a cache hit. If it doesn't, and turns to the system memory, this is called a cache miss. Naturally, the ideal scenario is that the CPU always finds whatever it's looking for in the L1 cache itself. However, even the L2 and L3 caches are significantly faster than the RAM to not cause any noticeable delay to the user.

CPU memory cache is designed to reduce system latency by providing access to faster and faster forms of memory caches. As RAM speed gets faster with the advancements in DDR5 RAM, the overall system latency is going down, but the onboard cache memory on CPUs remains a crucial factor in the entire equation.

How big a deal is cache memory on modern CPUs?

Should you obsess over it?

Almost all modern CPUs feature enough L1, L2, and L3 cache for every day-to-day operation. Besides, CPU cache memory isn't the only thing determining CPU performance. However, if you're looking for peak gaming performance and don't want to compromise at all, cache memory becomes more important than ever. Thanks to AMD's Ryzen X3D CPUs, the importance of the L3 cache in gaming performance has become a hot topic.

AMD processors like the Ryzen 7 5800X3D, Ryzen 7 7800X3D, and the Ryzen 7 9800X3D, among others, feature enormous amounts of fast L3 cache that allow them to reach FPS numbers not possible on non-X3D CPUs. This is what makes these processors the best CPUs for gaming, by far. So, in a nutshell, your gaming PC will be perfectly fine even without an AMD X3D CPU, but if you can get your hands on one, you'll not regret it, provided you're not a productivity fiend.