What is memory

In the structure of the computer, there is a very important part, is the memory. Memory is used to store programs and data of the parts, for the computer, with memory, only memory function, to ensure normal work. There are many kinds of memory, according to its use can be divided into main memory and auxiliary memory, main memory also called internal memory (memory, RTHK called memory).

Memory is also called main storage, is the CPU can directly address the memory space, made of semiconductor devices. Memory is characterized by a fast access memory rate. Memory is the main part of the computer, it is relative to the external storage. The programs that we normally use, such as Windows operating system, typing software, game software, etc., are generally installed in the hard disk, such as external memory, but only this is not the use of its functions, they must be transferred into the RAM to run in order to really use its function, we usually enter a paragraph of text, or play a game, In fact, it's all in memory. It's like in a study, the shelves and bookcases that store books are the equivalent of a computer's memory, and our working desk is RAM. Usually, we put a large amount of data stored on the memory, and put some temporary or small amount of data and programs on the RAM, of course, the quality of memory will directly affect the speed of the computer running.

Memory overview

Memory is where the program and the data are stored temporarily, such as when we are working on a document using WPS, when you are typing characters on the keyboard,

It is stored in memory, and when you choose to save it, the data in memory is stored in a hard (magnetic) disk. Before you understand it further, you should recognize its physical concepts.

Memory is generally used in semiconductor storage units, including random memory (RAM), read-only memory (ROM), and caching (cache). Just because RAM is one of the most important memory. (synchronous) SDRAM synchronous dynamic random access memory: SDRAM is 168 feet, this is the current Pentium and above the use of memory. SDRAM locks the CPU and ram together through an identical clock, allowing the CPU and RAM to share a clock cycle, working synchronously at the same speed, with each clock pulse rising along the data, increasing the speed by 50% faster than the Edo memory. DDR (DOUBLE data RATE) Ram:sdram's replacement product, he allows the clock pulse to rise along and down the transmission of data, so no need to increase the frequency of the clock to increase the SDRAM speed.

Read-only memory (ROM)

Rom means read only memory (read only Memory), when the ROM is manufactured, information (data or program) is deposited and permanently saved. This information can only be read out, generally not written, even if the machine power outage, the data will not be lost. ROM is typically used to store basic computer programs and data, such as BIOS ROM. The physical shape is generally a two-row direct-insertion (DIP) integration block.

Random Memory (RAM)

Random memory (Random Access Memory) indicates that data can be read from or written to. When the machine is powered off

When closed, the data stored in it is lost. The memory that we usually buy or upgrade is used as the memory of the computer, and the Memory Bar (Simms) is a small circuit board that centralizes the RAM integration block, which plugs into the memory slots in the computer to reduce the space occupied by the RAM integration block. At present, the common memory in the market has 1g/strips, 2g/, 4g/, and so on.

High-speed buffer memory (cache)

Cache is also the concept we often encounter, that is, the common view of the first-level cache (L1 cache), level two cache (L2 cache), three-level caching (L3) of this data, which is located between the CPU and memory, is a faster read and write than memory storage. When the CPU writes or reads data to memory, the data is also stored in the cache memory. When the CPU needs this data again, the CPU reads the data from the cache rather than the slower memory, and of course, if the required data is not in the cache, the CPU reads the data in memory.

Physical Memory and address space

Physical storage and storage address space are two different concepts. But because the two have a very close relationship, and both are

B, KB, MB, GB to measure the size of their capacity, so it is easy to create confusion in understanding. Beginners understand these two different concepts to help further understand the internal memory and the use of good internal memory.

Physical memory refers to the actual existence of the specific memory chip. For example, the memory chips on the motherboard and the ROM chip with the system BIOS, the display RAM chip on the display card and the ROM chip that displays the BIOS, as well as the RAM chips and ROM chips on the adapter cards are physical memory.

The storage address space refers to the range of the memory encoding (encoding address). Encoding is the allocation of a number to each physical storage unit (a byte), usually called "addressing." Assigning a number to a storage unit is designed to make it easier to find and read and write the data, which is called "addressing" (so someone also calls the address space the addressing space).

The size of the address space and the size of the physical memory are not necessarily equal. To illustrate this problem, for example, there are 17 rooms on a floor, numbered 801~817. The 17 rooms are physical, and their address space is three-bit encoded, with a range of 800~899 of 100 addresses, and the visible address space is larger than the actual number of rooms.

For 386 above grade microcomputer, its address bus select、read is 32 bits, therefore the address space can reach 2 32 times Square, namely 4GB. (although, however, some of the operating systems we typically use, such as Windows XP, can only recognize or use 3.25G of memory, the 64-bit operating system recognizes and uses more than 4G and 4G of memory,

Well, now you can explain why there are different types of memory such as conventional memory, reserved memory, upper memory, high memory, extended memory, and expanded memory.