RFL1, L2, and L3 Cache Memory: Understanding the Differences
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This article compares the different levels of cache memory: L1, L2, and L3. It will explain what they are and the key differences between them.
What is Cache?
In computing, cache is a type of high-speed memory designed to reduce the average time it takes to access data from main memory (RAM). It stores frequently used instructions or data, allowing the CPU to access them more quickly.
There are several types of cache, including:
- L1/L2/L3 cache: These are the main types we’ll be discussing.
- RAM cache: In essence, this is the same as CPU cache. L1/L2 caches data from RAM, while RAM caches data from the hard disk. For example, when Windows loads, it loads several required libraries into RAM.
- Disk cache: Similar to RAM cache, disk cache holds recently read or written data from a hard drive (HD). This speeds up subsequent reads of that data. Most modern hard drives have around 8 MB of cache memory.
- Software cache: Software often needs to cache data into RAM that it uses frequently. This data is often processed data from a file, translated by the program into another data structure. Examples include web browsers like Internet Explorer and games.
Cache memories are located closer to the CPU than RAM, and store recently accessed data from RAM. They hold instructions that are to be executed next and variables needed by the CPU.
Level 1 cache is stored on the CPU itself, while L2 and L3 caches are stored near, but not directly on, the CPU. L1/L2/L3 cache is generally more expensive than RAM.
L1 Cache Memory
- Location: On-chip (integrated directly into the CPU)
- Access Time: 2 to 8 nanoseconds (ns)
- Typical Sizes: 8 KB, 64 KB, 128 KB
- Technology: SRAM (Static RAM)
- Management: Hardware
L2 Cache Memory
- Location: Off-chip (located near the CPU, but not directly on it)
- Access Time: 3 to 10 ns
- Typical Sizes: 256 KB, 1 MB, 2 MB
- Technology: SRAM
- Management: Hardware
L3 Cache Memory
- Location: Off-chip
- Access Time: 10 to 20 ns
- Typical Sizes: 4 to 8 MB (laptop), 8 to 32 MB (desktop)
L1 vs L2 vs L3 Cache: Key Differences
The following table summarizes the differences between L1, L2, and L3 cache memory:
| Features | L1 Cache | L2 Cache | L3 Cache |
|---|---|---|---|
| Location | Directly built into the processor; stores CPU’s recently accessed information. | Located outside and separated from the CPU chip core. | Built on the motherboard within the CPU module; used by all cores. |
| Size | Smallest cache | Larger than L1 and smaller than L3 | Largest cache |
| Cache type/Name | Level 1, primary, or internal cache | Level 2, secondary, or external cache | Level 3 or external cache |
| Speed | Fastest cache | Slower than L1 but faster than L3 | Slowest cache |
| Use | Each core in the CPU has its own L1 cache memory | Each core in the CPU has its own L2 cache memory | All cores in the CPU share the same L3 cache memory |
