What is L1 L2 and L3 Cache

When checking the processor of a laptop or computer, you’ll often come across terms like L1, L2, and L3 cache.

Most people ignore this aspect because they aren’t familiar with it. They see it as a technical term without understanding its significance.

Should you also ignore it? No, you should not.

It is an important part of a CPU and plays a vital role in its speed and performance.

So, what is L1, L2, and L3 cache? Let’s find it out.

Introduction to Cache Memory

For easy understanding, the “L” stands for Level. So, L1, L2, and L3 are essentially three levels of cache.

To grasp the concept of L1, L2, and L3 caches, you need to understand what the CPU cache is.

So, before anything else, let’s learn about the CPU cache.

What is Cache Memory and Why It’s Important?

What is Cache Memory, What is L1 L2 and L3 Cache

For those who don’t know, there are two types of RAM:

  1. DRAM (Dynamic RAM)
  2. SRAM (Static RAM)

DRAM is a type of memory that uses capacitors to store data. These capacitors need to be constantly refreshed with electricity to retain the data.

SRAM, on the other hand, does not need to be constantly refreshed. It makes SRAM much faster than DRAM, but also more expensive.

SRAM is what is used in the CPU cache.

The CPU cache is the CPU’s internal memory. Its job is to copy and store data and instructions from RAM that are waiting to be used by the CPU.

Basically, what the CPU cache does is hold common data that it thinks the CPU will access repeatedly.

When the CPU needs data, it always checks the faster cache memory first. If the data isn’t there, the CPU has to access the slower primary memory, which is RAM or DRAM.

That’s why cache memory is so important, as it quickly transfers data to the CPU when needed.

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What is L1 Cache?

The primary cache memory in the CPU is the Level 1, or L1, cache.

The L1 cache is located directly on the processor itself, allowing it to run at the same speed as the processor. It is the fastest cache or fastest memory in a laptop or computer.

As modern CPUs have become incredibly fast, the L1 cache has also increased in speed to keep up.

What is L2 Cache?

The L2 cache, also known as Level 2 cache, is an external cache that is not located directly on the CPU.

It is used to store recent data accesses from the processor that were not caught by the Level 1 cache. L2 cache stores the data that might not fit into L1 cache.

If the CPU can’t find the data it needs in the L1 cache, it then searches the L2 cache. If the CPU can’t find the data in the L2 cache either, it then searches the last level of cache, which is the Level 3 cache.

It’s important to note that the L2 cache is also fast, but not as fast as the L1 cache. Because the L2 cache is located outside the CPU, it cannot match the speed of the CPU and L1 cache.

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What is L3 Cache?

The Level 3 (L3) cache is the final level of CPU cache, designed to store recent data accesses that were not captured by the Level 2 (L2) cache. You can also say that L3 cache stores the data that might not fit into L1 or L2 caches.

If the CPU doesn’t find the data in the L3 cache, it must retrieve it from the slower main memory, which is the RAM.

You might have heard that RAM is a fast memory, operating at much higher speeds than HDDs or even SSDs, which is why it is more expensive.

It is true, but there are even faster types of memory known as cache memory.

The L3 cache is significantly faster than RAM, although not as fast as the L1 or L2 caches.

How L1, L2, and L3 Cache Memory Helps the CPU?

How Cache Memory Helps the CPU, What is L1 L2 and L3 Cache

The primary purpose of the L1, L2, and L3 cache is to maximize the speed of a laptop or computer.

The L1 cache is the fastest because it is located directly on the CPU.

In future generations of processors, the L2 and L3 caches will also be integrated into the CPU to further enhance processing speed.

Now coming to the question, how do L1, L2, and L3 caches help the CPU?

Despite significant improvements in RAM speed, it still cannot supply data to the CPU quickly enough.

Modern CPUs are so fast that they often remain idle, waiting for data to process from slower RAM, which wastes their processing power.

Cache memory addresses this problem, as it acts as an intermediate between the CPU and RAM, supplying the CPU with data much more rapidly.

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What is a Good Cache Size?

The more you pay, the more you get.

In cheaper laptops, most CPUs have an L1 cache of around 192KB. In more expensive laptops or computers, the L1 cache can reach up to 512KB.

The L2 cache can range from 1MB to 4MB. While a 4MB L2 cache is typically found in higher-end systems, it is still available.

The L3 cache ranges from 4MB to 20MB.

A good cache size is:

  • L1 cache: 192KB to 512KB
  • L2 cache: 1MB to 4MB
  • L3 cache: 4MB to 20MB

You should know that companies generally advertise only the L3 cache because it is the largest cache.

Most users are not familiar with cache memory, and if they see a 512KB or smaller L1 cache, they might be disappointed, perceiving 512KB as very small by today’s standards.

Therefore, companies often highlight the L3 cache to provide a sense of ample memory size.

Additionally, the size of cache memory depends on the processor you choose. In cheaper processors, you might get lower cache memory, while in more expensive processors, you will get more cache memory.

In simple words, if you want more cache memory, you have to pay more.

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Thankfully, all laptops come with a decent amount of cache memory, so you don’t have to worry too much about cache size.

However, we still recommend checking the L1, L2, and L3 cache sizes because they are important.

If you are spending a significant amount, like $700 to $1000, and still getting a 192KB L1 cache, you should reconsider your purchase, as you should be getting more than 300KB of L1 cache in that price range.

A difference of around 100KB might not seem significant, but it actually is when it comes to processing performance.

So, while most laptops and computers come with sufficient cache memory, it’s still a good idea to check the specifications.

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1. Can a CPU run without cache memory?

Yes, a CPU can technically run without cache memory, but it would be incredibly slow, taking hours to perform even simple operations. Cache memory, like the L1 cache, is integrated into CPUs to prevent this sluggish performance and ensure your computer runs efficiently and quickly.

2. Why is L1 cache so small?

The simplest reason for the L1 cache being so small is both speed and cost. Because the L1 cache is extremely fast, it can process large amounts of data in milliseconds.

Its small size also allows for very low latency.

However, matching the L1 cache’s speed to the CPU’s speed is expensive. Therefore, making a few MB of L1 cache would significantly increase costs without providing proportional benefits.

3. What is the purpose of cache memory in a computer?

Cache memory stores frequently accessed data and instructions to speed up the overall performance of the computer by reducing the time it takes to access data from the main memory.

4. Why is L1 cache faster than L2 and L3 caches?

The L1 cache is the fastest because it is located closest to the CPU cores. To match the CPU’s speed, it is built using faster but more expensive memory technologies.

5. How does the size of each cache level impact performance?

The size of each cache level impacts performance by balancing speed and capacity. L1 cache is small but extremely fast, L2 is larger but slower, and L3 is the largest and slowest. Larger caches can store more data but take longer to access, while smaller caches are quicker but hold less data.

6. Can the cache memory size be upgraded?

No, cache memory size is integrated into the CPU architecture and cannot be upgraded separately. To get more cache, you need to upgrade to a CPU with more built-in cache.

7. What happens when the cache is full?

When the cache is full, the CPU uses cache replacement policies to determine which data to overwrite with new data. Common replacement policies include Least Recently Used (LRU) and First-In-First-Out (FIFO).

8. Are there differences in cache implementation across different CPU architectures?

Yes, different CPU architectures may implement cache hierarchies differently, including variations in size, speed, and levels of cache. For example, ARM processors might have a different cache configuration compared to x86 processors.

So, what is L1, L2, and L3 cache? What are they used for? We are sure you know the answer now.

If you still have any doubts, feel free to ask us in the comment section.

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