Urgent!!! What are the similarities and differences between cache and virtual storage in principle a

Cache is physical storage The previous memory speed was very slow, so it was very slow when exchanging data with the processing area, which caused the machine to run very slowly, so this thing was born, because the speed of memory reading is relatively fast, so he first put the data in the memory into the cache Cache is very fast, so the processing speed will be accelerated for a long time! Wait until you're done and go back to memory! This solves the bottleneck that greatly affects the processing speed due to the memory transfer speed!

Virtual memory is a part of your hard drive that acts as a data relay! Let's say you're running out of memory! The system automatically stores the data that is not used for the time being on the hard drive, so that there is enough space in the memory to run other programs!

Cache was introduced to alleviate the difference in read and stored data between the CPU and memory. The current cache is generally at the kilobyte level. Cache is slowly being integrated into the CPU.

Virtual memory, such as virtual memory, is actually a portion of the hard disk that is used as memory. When your physical memory usage is too high, the system will automatically call your virtual memory to transfer part of the memory data to the virtual memory to free up space for the memory.

Cache is a cache, which is used to buffer data between CPU and memory, and virtual storage is just storage.

First of all, they are both memory, which is their main similarity.

Cache is commonly referred to as caching SRAM. SRAM is called static memory, and "static" means that when we write a piece of data to SRAM, the written data remains unchanged unless new data is rewritten or the power is turned off. Since the speed of the CPU is much faster than the speed of the memory and hard disk, it will cause the CPU to wait when accessing data, affecting the speed of the computer.

SRAM accesses faster than other memory and hard disks, so it is used as a cache for computers.

With the cache, you can pre-write the data to it first, and read it directly from it when needed, which shortens the CPU waiting time. The reason why the cache can improve the speed of the system is based on a statistical law, the control system on the motherboard will automatically count which data in the memory will be used frequently, and store the data in the cache, and when the CPU wants to access the data, it will first go to the cache to find it, so as to improve the overall running speed. Generally speaking, the 256K cache can increase the speed of the whole machine by about 10% on average.

The so-called virtual memory is to unify the use of internal and external memory, and the basic idea is to keep the part that is being used in memory. The capacity of the virtual memory is related to the address structure of the CPU, such as the address bit of the Pentium is 32 bits, then his addressing space is 2 to the 32nd power, 4GB, that is, his maximum addressing space is 4GB.

Cache and vmem data are stored on the memory, taking memory as an example, cache is generally some temporary data, once the program is run, or the operating system exits, or power off, the data is gone, vmem is equivalent to the memory as a hard disk, when reading, the data is read from the hard disk to the memory, and the read and write operations are to read and write the memory as a hard disk, which greatly improves the reading and writing efficiency. When the program exits, the data is written back to the hard drive, or when the system is not busy.

Cache, commonly known as cache, storage speed is a storage medium between memory and CPU, so that the internal memory is used to solve the speed mismatch between memory and CPU; Virtual storage generally refers to storage devices, such as disk arrays, which belong to external storage devices. Another is virtual memory, which is a part of the hard disk that is divided into a part of the disk to store frequently used data, solving the speed mismatch between memory and disk.

Similarities: The most recently used part of the program resides in high-speed memory;

Once these parts become incommon, send them back to the low-speed memory;

This swap-in and swap-out is done by the hardware or operating system and is transparent to the user;

Attempt to make the storage system's performance close to that of high-speed memory,**close to that of low-speed memory.

The main difference: the performance penalty of a miss in the virtual storage is much greater than the loss of a miss in the cache system.

Staging data for the processor, waiting for calls.

In fact, there are also in the encyclopedia

The cache has three parts:

cache: The main storage is stored by the main memory.

Incoming instructions and data blocks.

Virtual memory: Also known as virtual memory

memory）。All programs running on the computer need to be executed through memory, and if the program is large or numerous, it will cause the memory to be exhausted. To solve this problem, virtual memory technology is used in Windows, that is, a portion of the hard disk space is used as memory usage.

When the memory is depleted, the computer will automatically call the hard disk to act as memory to relieve the strain on memory. If the computer lacks RAM to run programs or operations.

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It will be used to compensate. It combines your computer's RAM with the temporary space on your hard drive. When RAM runs slowly, it moves data from RAM into a space called a "paging file".

Moving data in and out of a paging file frees up RAM so you can get the job done.

Generally speaking, the more RAM a computer has, the faster the program will run. If your computer's speed is slowed down due to lack of RAM available space, you can try to compensate by adding virtual memory. However, computers can read data from RAM at a faster rate than from a hard drive, thus increasing the RAM capacity (memory modules can be added).

is the best choice. Reference.

Similarities: Substitution between memory and external memory, and between memory and cache, both require high hit ratios, and both need to divide the storage area into smaller modules.

Differences: The replacement speed between memory and external memory is much smaller than the replacement speed between cache and memory, so the module that is replaced between memory and external memory at one time is larger, and it generally adopts the mapping method of segment page, while the group association mapping mode is mostly used between cache and memory!