Cache size is one of the important indicators of the CPU, its structure and size have a great influence on the CPU speed. Simply put, the cache is used to store some commonly used or upcoming data or instructions. When the data or instructions are needed, they can be read directly from the cache. This is much faster than reading from the memory or even the hard disk. Significantly increase the processing speed of the CPU.
The so-called processor cache, usually refers to the second-level cache, or external cache. That is, the cache, which is a relatively small but very high-speed memory located between the CPU and the main memory DRAM (Dynamic RAM), is usually composed of an SRAM (Static Random Access Memory). Used to store data that is frequently used by the CPU so that the CPU does not have to rely on slower DRAM (Dynamic Random Access Memory). L2 caches are always a type of memory that is extremely fast and expensive, called SRAM (Static RAM), and SRAM (Static RAM) is the abbreviation for Static Memory. Since the SRAM uses the same semiconductor technology as the production CPU, compared with the dynamic memory DRAM, the access speed of the SRAM is fast, but the size is large and the price is high.
The basic idea of ​​the processor cache is to use a small amount of SRAM as a buffer between the CPU and the DRAM memory system, ie the Cache system. One notable feature of the 80486 and higher-end microprocessors is that the processor chip integrates SRAM as a Cache. Because these Caches are mounted in the chip, the capacity of the Cache, which is called on-chip Cache.486, is usually 8K. Pentium is 16KB and Power PC is up to 32KB. The Pentium microprocessor further improves on-chip Cache, uses data and dual-channel Cache technology. Relatively speaking, on-chip Cache is not large, but it is very flexible, convenient, and greatly improved. Microprocessor performance. On-chip Cache is also referred to as Level 1 Cache. Because the clock frequencies of high-end processors such as 486, 586 are very high, once a Level 1 Cache miss occurs, the performance will deteriorate significantly. The approach taken in this case is to add a Cache outside the processor chip, called a secondary cache. The secondary cache is actually a buffer between the CPU and main memory. Because the response time on the system board is much lower than the speed of the CPU, if there is no secondary cache, it is impossible to achieve the ideal speed of high-end processors such as 486, 586. The capacity of the secondary cache is usually more than one order of magnitude greater than that of the primary cache. In the system settings, the user is often required to determine whether the secondary cache is installed and its size is large. The size of the secondary cache is generally 128 KB, 256 KB, or 512 KB. Among the microcomputers in the 486 or higher class, 256 KB or 512 KB synchronous cache is commonly used. The so-called synchronization refers to that the Cache and the CPU use the same clock cycle and work synchronously at the same speed. Compared to asynchronous Cache, performance can be increased by more than 30%.
At present, one of the trends in the development of PCs and their server systems is that the higher the CPU frequency is, the more advanced and more advanced the system architecture, and the slower the improvement of the structure and access time of the main memory DRAM. Therefore, the Cache technology is becoming more and more important, and the Cache is getting bigger and bigger in the PC system. The majority of users have used Cache as an important indicator for evaluating and purchasing PC systems.