Memory will not work! CPU cache is so important

How much computer memory is enough? Today, 8GB is the starting point, but 16GB is more than sufficient for most users. What about speed? DDR4 2666 is definitely a solid choice. However, do you know that even though memory is much faster than hard drives, it's still relatively slow compared to the CPU? When the CPU and memory exchange data, the CPU's internal cache plays a crucial role. Today, we'll dive into what the CPU cache is and why it matters.

What is CPU Cache?

Modern computer memory, even high-speed RAM like Intel's Optane, isn't as fast as the cache inside the CPU. The size and design of the cache are also key performance indicators of a CPU. It acts as a temporary storage that allows the CPU to access frequently used data quickly, improving overall system performance.

The first thing to understand is the cache operating frequency. The cache runs at the same frequency as the CPU, which reduces bottlenecks in I/O operations because it's located inside the processor. As a result, the CPU cache is far more efficient than both memory and hard drives, and it operates at a completely different level.

So how does the cache work? When the CPU needs to read data or perform calculations, it first checks the internal cache. If the data is there, it can be accessed at the fastest speed possible. If not, the CPU will retrieve the data from the main memory through the cache and then send it back to the CPU for processing. Additionally, the surrounding data is also cached, so future reads of that block can be done directly from the cache without accessing the slower memory.

Why Do We Need Three Levels of Cache?

CPU - cache - memory is the general workflow. To further optimize data scheduling, the CPU cache is divided into multiple levels, improving throughput, temporary storage, and execution efficiency.

L1 Cache

The first-level cache (L1) is the closest to the CPU core and is responsible for storing both data and instructions. L1 cache has a significant impact on CPU performance due to its structure and capacity. However, because of its complexity, it’s typically limited to around 256KB in most CPUs.

L2 Cache

The second-level cache (L2) is larger than L1 and directly affects CPU performance. The bigger the L2 cache, the better. For example, an 8th-generation Core i7 8700 has 256KB of L2 cache per core, totaling 1.5MB across all six cores. This makes it exclusive to each core, optimizing performance for multi-threaded tasks.

L3 Cache

The third-level cache (L3) was originally designed for server CPUs but is now commonly found in consumer-grade processors. Its main purpose is to reduce memory latency and improve performance when dealing with large amounts of data. Unlike L2, L3 is shared among all cores and can have a very large capacity, often reaching several megabytes.

While clock speed and core count are key factors in CPU performance, the cache plays an equally important role in making the CPU smarter and more efficient. Both Intel and AMD have been increasing their L3 cache sizes over time, especially to enhance the gaming experience and user satisfaction. Whether you're a casual user or a power gamer, understanding your CPU's cache can help you make better hardware choices.