ZisaLog: Beginner’s Guide to Building a Custom PC 
Cache memory refers to the memory built into the CPU, and it plays an important role in improving the processing speed of a computer.
However, when choosing a CPU, cache memory performance is generally not the main criterion, so for those building a custom PC, it is enough to know only the key points about cache memory.
Still, for those who want to understand how computers and CPUs work, this is valuable information worth reading.
- Cache memory is a high-speed memory that temporarily stores data and instructions frequently accessed by the CPU
- Role 1: Shortens data read/write time to improve processing speed
- Role 2: Efficiently uses main memory bandwidth to improve processing speed
- Cache memory is divided into L1, L2, and L3, each with different capacity, speed, and design.
This article also explains basic knowledge such as how to read CPU manufacturer and model numbers, performance indicators, and how to choose a CPU from the perspectives of performance and compatibility.
≫ Related article: How to Choose a CPU for a Custom PC [Performance / Features / Compatibility]
Select PC parts and online stores to instantly generate an estimate, check compatibility, and calculate power requirements. You can save up to five different builds, making it easy to try out multiple configurations.
≫ Tool：PC Parts Estimation & Compatibility Check Tool
Table of Contents
What is CPU Cache Memory?
This section explains the basics of CPU cache memory.
The Role of Cache Memory
Cache memory is high-speed memory that temporarily stores data and instructions frequently accessed by the CPU.
This allows the CPU to read necessary data from the faster cache memory instead of directly from the main memory (RAM).
As a result, the time required for data read and write is reduced, and overall processing speed is improved.
Cache memory is usually located inside the CPU and has a hierarchical structure such as L1 cache, L2 cache, and L3 cache.
L1 cache is the fastest and is located closest to the CPU core.
L2 and L3 caches are slightly slower but have larger capacities.
This hierarchical structure allows the CPU to access data in the most efficient way.
Another important role of cache memory is efficient use of memory bandwidth.
With cache memory, the CPU does not need to read the same data from main memory repeatedly, preventing wasteful use of memory bandwidth.
This improves the overall performance of the computer.
Difference Between Cache Memory and Main Memory
Since main memory also temporarily stores data, some may wonder what the difference is.
The main differences between cache memory and main memory are their roles and speed.
Difference in Roles Between Cache Memory and Main Memory
As mentioned earlier, the main role of cache memory is to reduce access time to main memory and make data usage more efficient.
On the other hand, main memory holds the data and code needed during program execution and allows the CPU and other PC parts to access them quickly.
Compared to cache memory, main memory exchanges data with various parts (GPU, storage, chipset, peripherals), so its bandwidth cannot be used only for the CPU.
Therefore, cache memory is prepared as dedicated memory for the CPU, and by handling frequently accessed data, it reduces the load on main memory and helps smooth data exchange with other parts.
Difference in Speed Between Cache Memory and Main Memory
Cache memory is extremely fast and can transfer tens to hundreds of GB per second.
On the other hand, main memory has a larger capacity than cache memory, but its speed is slower, at tens of GB per second.
*The speed varies depending on the CPU and memory, so this is a rough comparison.
About CPU Cache Speed, Design, and Structure
Cache memory has three levels: L1 cache, L2 cache, and L3 cache, each with different speeds and capacities.
L1 cache is the fastest and closest to the CPU core, but has the smallest capacity.
L2 cache is slightly slower than L1 but has a larger capacity.
L3 cache is even slower, but is often shared among multiple CPU cores and helps improve overall efficiency.
When these cache memories work efficiently, the CPU’s processing speed increases significantly, improving the overall performance of the computer.
| Memory Type | Features | Capacity | Independent/Shared |
|---|---|---|---|
| L1 Cache | – Ultra-fast and small capacity – Located inside the core and very close – Divided into data cache and instruction cache | 32KB–96KB (per core) | Independent per core |
| L2 Cache | – Fast and medium capacity – Located inside the core and relatively close | 512KB–4MB (per core) | Independent per core |
| L3 Cache | – Large capacity and medium speed – Located outside each core and a bit farther | 16MB–64MB | Shared among multiple cores |
| Main Memory | – Large capacity but slow | Several GB to tens of GB | Shared by the whole system |
L1 Cache
L1 cache is the fastest and smallest cache memory inside the CPU.
Each CPU core has its own dedicated L1 cache, which mainly stores frequently used data and instructions.
This greatly reduces the time the CPU needs to access main memory and improves overall processing speed.
Also, by design, L1 cache is often divided into instruction cache and data cache, and each operates independently, allowing for more efficient data processing.
Therefore, the total L1 cache capacity is calculated as: capacity per cache × number of cores × 2 (for instruction and data).
Data Cache
The data cache (L1 Data Cache) is a cache that temporarily stores data frequently accessed by the CPU.
It is used to speed up data read and write from memory.
Each core has its own dedicated data cache, and they operate independently.
Instruction Cache
The instruction cache (L1 Instruction Cache) is a cache that temporarily stores program instructions executed by the CPU.
It is used to speed up the fetching of program instructions.
Each core has its own dedicated instruction cache, which also operates independently.
*Fetching refers to the process of the CPU obtaining the next program instruction to execute.
Why Separate Data Cache and Instruction Cache?
The design of separating data cache and instruction cache is for improving simultaneous access efficiency and easier optimization.
The CPU often fetches instructions while reading and writing data, so having separate caches for data and instructions reduces conflicts and improves efficiency for parallel access.
Also, the access patterns for data and instructions are different, so each can be optimized separately.
When accessing data, the program often accesses various locations in memory randomly (random access).
In contrast, program instructions are usually fetched sequentially (sequential access).
Because the optimal design is different, separating data cache and instruction cache allows for more efficient data processing.
L2 Cache
L2 cache has a larger capacity than L1 cache and is used when L1 cache cannot find the required data.
It is located between the CPU core and main memory and acts as an intermediate layer to speed up data read and write.
This reduces the frequency of the CPU accessing main memory and improves overall processing speed.
The capacity and speed of L2 cache vary depending on the CPU design, but it is generally several hundred KB to several MB.
Like L1 cache, L2 cache is often dedicated to each CPU core.
L3 Cache
L3 cache has the largest capacity and the slowest access speed among CPU cache memories.
While L1 and L2 caches are dedicated to each CPU core, L3 cache is shared among multiple cores.
L3 cache is relatively slow, but its large capacity allows it to store more data.
This makes data exchange between cores more efficient and reduces the number of accesses to main memory, improving overall performance.
How to Check CPU Cache Memory Capacity
This section explains how to check the capacity of cache memory.
How to Check the CPU Installed in Your PC
To check the cache memory of the CPU used in your PC, use software that can display hardware information.
For example, Task Manager, CPU-Z, and Speccy are all free to use.
Using Task Manager
If you only want to check the cache memory capacity, Task Manager is the quickest way.
To open Task Manager, right-click the taskbar and select [Task Manager].
Select [CPU] under the [Performance] tab, and cache information will appear at the bottom right.
However, note that the total capacity for L1 and L2 caches is displayed, even though they are divided per core.
Using CPU-Z
You can check under the [Cache] section of the [CPU] tab.
| Cache Type | Cache Capacity | Data Arrangement |
|---|---|---|
| L1 Data | 4×32 KByte | 8-way |
| L1 Inst. | 4×32 KByte | 8-way |
| Level 2 | 4×256 KByte | 4-way |
| Level 3 | 8MByte | 16-way |
You can also check the cache capacity per core and the separate capacities for L1 data and instruction caches.
Using Speccy
For Speccy, the cache information is listed under [CPU] in the left menu.
How to Check CPU Specifications
If you want to check cache memory before buying a CPU, check the product specifications.
Let’s use the Intel Core i7-14700F as an example.
When checking the official specifications, there are two items: [Cache] and [Total L2 Cache].
Cache refers to the L3 cache capacity.
Total L2 Cache refers to the total capacity of the L2 cache.
For some reason, information about L1 cache is not listed in the official product specifications and can only be known after purchase.
Also, AMD’s product specifications list the total capacities for L1, L2, and L3 caches.
Summary: Delivering Data and Instructions to the CPU Faster Than Main Memory
This article explained the role of CPU cache memory, the differences from main memory, the hierarchical structure of cache, and how to check cache information.
When choosing a CPU for a custom PC, cache memory capacity is not usually a concern, but learning about how computers and CPUs work can be valuable.
Ken-san
Here is a summary of the key points about CPU cache memory.
- Cache memory is a high-speed memory that temporarily stores data and instructions frequently accessed by the CPU
- Role 1: Shortens data read/write time to improve processing speed
- Role 2: Efficiently uses main memory bandwidth to improve processing speed
- Cache memory is divided into L1, L2, and L3, each with different capacity, speed, and design.
The design of adding memory not only to main memory but also to the CPU to improve the overall performance of the computer is truly well thought out.
It might be interesting to check the cache memory information of your own computer once.
This article also explains basic knowledge such as how to read CPU manufacturer and model numbers, performance indicators, and how to choose a CPU from the perspectives of performance and compatibility.
≫ Related article: How to Choose a CPU for a Custom PC [Performance / Features / Compatibility]
Select PC parts and online stores to instantly generate an estimate, check compatibility, and calculate power requirements. You can save up to five different builds, making it easy to try out multiple configurations.
≫ Tool：PC Parts Estimation & Compatibility Check Tool
