What is the difference between cached and available memory

1. CPU cache (cache memory) is located in the temporary memory between the CPU and the memory, its capacity is smaller than the memory but the exchange speed is faster. The data in the cache is a small part of the memory, but this small part is about to be accessed by the CPU in a short period of time, and when the CPU calls a large amount of data, it can be called directly from the cache without memory, thus speeding up the read speed. It can be seen that adding a cache to the CPU is an efficient solution, so that the entire internal memory (cache + memory) becomes a high-speed storage system with both cache and large capacity of memory.

Caching has a significant impact on CPU performance, mainly due to the order in which the CPU exchanges data and the bandwidth between the CPU and the cache.

2. The working principle of the cache is that when the CPU wants to read a data, it will first find it from the cache, and if it finds it, it will be read immediately and sent to the CPU for processing; If it is not found, it is read from the memory at a relatively slow speed and sent to the CPU for processing, and at the same time, the data block where the data is located is called into the cache, so that the entire block of data can be read from the cache in the future, and the memory does not need to be called.

The cache is the space on the hard disk that is being called, which is called if the actual memory in your memory module runs out. When the computer uses the cache, it means that it is running overloaded.

Cache and memory are different components of a computer.

1. Due to the factor of CPU chip area and cost, the cache is very small. Now the general cache is only a few M, and the running frequency of the cache in the CPU is extremely high, generally operating at the same frequency as the processor, and the work efficiency is far greater than that of the system memory and hard disk. In practice, the CPU often needs to read the same data block repeatedly, and the increase of the cache capacity can greatly improve the hit rate of the CPU's internal read data, instead of searching for it in memory or hard disk, so as to improve system performance.

2. Memory, also known as internal memory, is used to temporarily store computing data in the CPU and exchange data with external memory such as hard disks. As long as the computer is running, the CPU will transfer the data that needs to be calculated to the memory for calculation, and when the operation is completed, the CPU will send the result out, and the operation of the memory also determines the stable operation of the computer.

The cache is a temporary storage place, and memory can be regarded as a relatively fixed storage place. But it's all about speeding up the computer and reducing the use of other parts.

The cache is built inside the CPU.

The memory is on the motherboard.

The read speed of the cache is dozens of times faster than that of memory.

These are two completely different concepts.

Memory is the space that the computer must occupy to run a program, and if the computer does not run a program, the corresponding space will be allocated in memory for the process, that is, the memory size, if it is not enough, it will be allocated from the should, which is called virtual memory.

The CPU cache is determined when the CPU is constructed, and the operation of all hardware and software in the computer must be controlled by the CPU, and of course, the data transmission between the CPU and each component also needs a temporary channel, which is the case, which is usually the CPU Level 2 cache.

But caching is many times faster than memory.

The specific speed is compared to the CPU cache >> memory >> hard drive.

Memory is internal memory and is a hardware device; Caching is a relatively large concept that is used to pre-read information (such as the cache of a hard disk), or to temporarily store some information that is not long-lasting.

1. "Memory" is like the memory system of the human brain, which is used to store the running programs and processed data of the computer, whether you turn on the power to start the computer or not, there will always be a variety of data information in the memory, and it can be said that it will never be idle.

2. When running a computer program, the program will first be read into memory, and then start executing in a specific memory, and the results of processing will also be saved in the memory, that is to say, the memory will always exchange data frequently with the CPU, without memory, the work of the CPU will be difficult to carry out, and the computer will not be able to start.

3. "Cache", the computer of the current town guess generation has both L1 and L2 cache. You may have heard your best friend advise you when buying a computer, "Don't buy a Celeron processor because it has less cache."

4. In computer systems, caching plays a pivotal role in many aspects, and it exists in various forms in different hardware. Among them, there are memory caches, hard disk and floppy disk caches, software disk caches, and page caches. Virtual memory is also a different form of cache.

Categories: Computer, Networking, >> Hardware.

Analysis: The main hardware of the computer, the hard disk, the speed between the memory and the processor is not the same, the speed of the processor is very fast, the memory is second, and the speed of the hard disk is very slow (relative to the processor), the processing of a task should be through the instructions given by the processor, the relevant data is called out of the hard disk, to the memory, there will be a lot of data transmission between the memory and the processor, the memory itself can not process the data, it must be processed by the processor, when they work together, Because the processor and memory work fast, they often have to wait for the hard disk to get things done, which greatly reduces the overall performance of the system and does not play the performance of all the hardware. In order to solve this problem, an excellent operating system must have a "cache" as an intermediate station between these hardware, to alleviate this contradiction, so as to improve the performance of the system to a certain extent, the better the "cache" is processed, the better the performance of the system.

From a certain point of view, the memory itself is a cache between the hard disk and the processor, and its role is to alleviate the sharp contradiction between the hard disk and the processor. When it is treated as a fixed component, it becomes an object in its own right that needs to be cached to alleviate bottlenecks. It is the only way for them to be sandwiched between the processor and the hard disk, and the relationship between the hard disk and the processor becomes a dual relationship between the hard disk and the memory and the memory.

The most "famous" cache is the page file, this is not to alleviate the speed, but to alleviate the capacity, in terms of speed, the hard disk is not as good as the memory, but in terms of capacity, the memory is impossible to compare with the hard disk, when you run a program needs a lot of data, occupy a lot of memory, the memory will be filled, what to do? Put those that are not used in the hard disk for the time being, because the processor always only calls the data required to process a task, and the other prepared data (that is, those that may be used by the backbone, but are not used for the time being) can be put first, if it cannot be stored, it has to be put on the hard disk. But this comes at a cost, and when the data put into memory is ready to be used again, you have to wait a long time for the system to bring up the data on the hard drive.

In fact, you can feel these actions of the system, for example, if you open IE or Office, the first time you open it is very slow, but it is much faster to open it again immediately after closing, this is because the data has not been "invited" out of the memory by the system at this time, and it is naturally faster for Sakura and Niantong to get data directly from the memory; In another case, when you open a big software like Photoshop, it will be a little slower than usual to open Office, this is because the memory is occupied by Photoshop, and if you want to call the data of Office to the memory, you must "please" the data of Photoshop out of the memory.

First, the meaning is different:

Memory is internal memory.

is a hardware device; Caching is a relatively large concept that is used to pre-read information (such as the cache of a hard disk), or to temporarily store some information that is not long-lasting.

Second, the use is different:

Memory is like the memory system of the human brain, which is used to store the running programs and processed data of the computer, whether the power is turned on or not to start the computer, there will always be all kinds of data information in the memory, it can be said that it will never be idle.

Cache, modern computers have both L1 and L2 caches. You may have heard a good friend advise you when buying a computer, "Don't buy a Celeron."

celeron) series of processors, because it has less cache".

How it works. Caching works by first caching from the CPU when it wants to read a piece of data.

If you find it, you will immediately read it and send it to the CPU for processing; If it is not found, it is read from the relatively slow memory and sent to the CPU for processing, and the data block where the data is located is called into the cache, so that the entire block of data can be read from the cache in the future, and the memory does not need to be called.

It is this read mechanism that makes the CPU read cache have a very high hit ratio, which means that 90% of the data that the CPU will read next time is in the CPU cache, and only about 10% needs to be read from memory. This greatly saves the time for the CPU to read the memory directly, and also makes it basically unnecessary for the CPU to wait for the CPU to read the data.

The above content reference: Encyclopedia - Cache.