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Cache

An important concept related to processor speed is keeping data flowing into the processor. Registers are a type of high-speed memory storage inside the processor. They are used to temporarily hold calculations, data, or instructions. The data or instruction the CPU needs to operate on is usually found in one of three places: cache memory, the motherboard memory (main memory), or the hard drive.

Cache memory is a very fast type of memory designed to increase the speed of processor operations. CPU efficiency is increased when data continuously flows into the CPU. Cache provides the fastest access. If the information is not in cache, the processor looks for the data in motherboard RAM. If the information is not there, it is retrieved from the hard drive and placed into the motherboard memory or the cache. Hard drive access is the slowest of the three. Table 3.2 lists the types of cache.

TABLE 3.2 Types of cache

Type

Explanation

L1 cache

Cache memory integrated into the processor

L2 cache

Cache in the processor packaging, but not part of the CPU; also called on-die cache

L3 cache

Usually found in the more powerful processors and can be located in the CPU housing (on-die) or on the motherboard

An analogy best explains this. Consider a glass of cold lemonade, a pitcher of lemonade, and a can of frozen lemonade concentrate. If you were thirsty, you would drink from the glass because it is the fastest and most easily accessible. If the glass were empty, you would pour lemonade from the pitcher to refill the glass. If the pitcher were empty, you would go to the freezer to get the frozen concentrate to make more lemonade. Figure 3.6 shows this concept.

Figure 3.6

Figure 3.6 CPU data sources

Usually, the more cache memory a system has, the better that system performs, but this is not always true. System performance also depends on the efficiency of the cache controller (the chip that manages the cache memory), the system design, the amount of available hard drive space, and the speed of the processor. When determining memory requirements, you must consider the operating system used, applications used, and hardware installed. The Windows XP operating system takes a lot less memory than Windows 10. High-end games and desktop publishing take more RAM than word processing. Free hard drive space and video memory are often as important as RAM in improving a computer’s performance. Memory is only one piece of the puzzle. All of the computer’s parts must work together to provide efficient system performance. Figure 3.7 shows this hierarchy of data access for the CPU.

Figure 3.7

Figure 3.7 Data access hierarchy

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