Cache is a computing component, both hardware and software, that stores data in order to serve future requests more quickly. This data may be the result of a computation that happened in the past or may be a copy of data that is stored elsewhere. Regardless of its origin, cache memory is an important component of your computer system.
Level 1 cache
The CPU has two levels of cache memory: the Level 1 cache and the Level 2 cache. When a CPU core needs a block of data, it first requests that block from the L1 cache. If the block is not present in the L1 cache, the CPU core fetches the data from the L2 cache and places it into the L1 cache.
The size of the Level 2 cache varies depending on the CPU, but it typically ranges from 256KB to 8MB. It is smaller than the Level 1 cache, and is typically much faster than system RAM. The L2 cache has a higher capacity and a faster response time than the Level 1 cache.
A CPU’s access latency is critical when reading data from the L1 cache. A latency of one ns or more can cause a CPU to take twice as long as it should, reducing performance by up to 14 percent. The use of high-speed SSDs and low-latency DDR4 RAM can minimize this impact on performance.
In a PC, the Level 1 cache is a small, embedded memory that holds data accessed recently. The Level 2 cache, or secondary cache, is stored in a separate memory chip that is close to the CPU. This type of memory is generally more expensive than RAM, but it can save a computer a great deal of time.
The L1 cache consists of two parts: data and instructions. The L2 cache is used for data only. In the past, CPUs used processors with different cache memory sizes. However, the recent trend is to consolidate all memory caching onto the CPU. This eliminates the need for specific motherboards and bus architectures.
Level 1 cache memory uses two transistors for every bit. It can store data without the assistance of external devices and can retain the data for longer periods of time than dynamic RAM. In comparison, dynamic RAM must be refreshed many times a second. Some CPUs use a 64KB Level 1 cache. The CPU can also use more than one cache if it is multi-core.
Programmers can optimize their use of the Level 1 cache by organizing access patterns and assigning virtual colors to virtual pages to avoid capacity misses. This technique avoids the possibility of running out of cache memory. However, this strategy does not work when the program needs to access more than one virtual page at a time. In order to optimize the use of the cache, programmers should arrange their code so that no two pages share the same virtual color.
Unlike L1 and L2, the L3 cache is usually shared among all CPU cores. This specialized cache is much faster than the Level 1 cache. It is the largest of the three cache levels. The L3 cache also improves the performance of the L1 and L2 cache. It is faster than RAM memory but is not as fast as Level 1.
The L1 cache has two parts, the data cache and the instruction cache. The L1 cache stores information used by the CPU and is often referred to as the primary cache. The L2 cache is larger than the L1 cache but smaller than L3. The L3 cache is built onto the motherboard as part of the CPU module.
In some cases, two copies of a main memory location can be kept in the cache. The simplest scheme is to use the least significant bits of the index of the memory location. The most common scheme makes use of two entries for a single memory location. Typically, the least significant bits are used to index data and tag SRAMs.
Modern processors have up to 512 KB of L1 cache memory per core. But server parts typically have twice that amount. The L2 cache is larger, but slower than the L1 cache. Most flagship CPUs contain four to eight megabytes of L2 cache memory. However, L2 caches are less expensive and may contain up to 256 KB of data per core.
Cache memory is an essential part of every computer. It stores data that the processor uses frequently. It also helps maintain the balance between main memory and processor speed. Because the processor is faster, the main memory has slower speeds. Cache memory helps to balance the two. If a processor requires more memory, it can use the L1 cache as a resource.
