Features
Random access
so-called "random access" refers to the desired time when data in the memory is read or written, The time is independent of the location of this information or the location written. When the information in the Sequential Access storage device is related, the time is related to the location of the information stored in the sequenceial access. It is mainly used to store operating systems, various applications, data, etc.
Volatile
RAM cannot retain data when the power is turned off. If you need to save the data, you must write them in a long-term storage device (eg hard drive). Compared to RAM, the maximum difference between the two is that the data saved above after the RAM will automatically disappear, and the ROM does not disappear, and it can be saved for a long time.
For static sensitive
as other fine integrated circuits, random access memory is very sensitive to the environmental static charge. Static electricity interferes with the charge of the memory capacitor, causing data loss, and even burnback circuits. Therefore, before the random access memory, you should touch the metal ground by hand.
Access Speed
Modern Random Access Memory is almost the fastest, access delay, and other storage devices related to mechanical operations in all access devices Comparison, it also appears insignificant.
Need to refresh (regenerated)
modern random access memory rely on capacitor storage data. The capacitor is filled with a representative 1 (binary), and is not charged. Data will gradually lose over time due to the case of the capacitor or less leakage. Refresh is the state of reading the capacitor in the specified period, and then recharged according to the original state to charge the capacitor to compensate for the lost charge. It is necessary to refresh that exactly the volatility of the random access memory.
Category
Depending on the working principle of the memory cell, the RAM is divided into static RAM and dynamic RAM.
Static Random Memory (SRAM)
The static storage unit is configured on the basis of a static trigger. Therefore, it is stored in the self-policy function of the trigger.
Dynamic Random Memory (DRAM)
The storage matrix of dynamic RAM is composed of a dynamic MOS storage unit. The dynamic MOS storage unit stores information using the gate capacitance of the MOS tube, but since the capacitance of the gate capacitance is small, the leakage current is not absolutely equal to 0, so that the charge preservation is limited. In order to avoid the loss of storage information, it is necessary to replenish the electric charge to the capacitor. This operation is usually referred to as "refresh" or "reproduction", so the DRAM is to be refreshed, and its operation is complicated than static RAM. Despite this, since the structure of the DRAM storage unit can be made very simple, the components used are less, the power consumption is low, and has become a mainstream product of large-capacity RAM.
Composition
RAM circuit consists of three parts: address decoder, storage matrix, and read / write control circuitry, as shown in Figure 1. The
memory matrix is arranged by the trigger, each trigger can store a bit data (0 or 1). Each set of memory cells is usually included as an address, stored a "word"; the number of bits of each word is equal to the number of this set of units. The capacity of the memory is represented by a "word number × bit". The address decoder translates each input address code to a high (or low) level signal, select a set of units from the storage matrix to turn on the read / write control circuit. Under the cooperation of the read and write control signal, the data is read or written.
Difference
read-only memory
ROM-Read Only Memory read-only memory: Simply, in the computer, RAM, ROM is a data store. RAM is a random access memory, and it is characterized by volatile, that is, the electricity and loss of electricity. ROM usually refers to curing memory (written, read repeatedly), which is the opposite of RAM. The ROM is divided into one-time curing, light erase and electric rubbing to rewrite three types. For example, if the file is turned off if you suddenly power out or not saved, the ROM can randomly save the previously available files but the RAM will disappear before the previously saved file.
Memory
In the composition structure of the computer, there is a very important part, that is, the memory. The memory is a component for storing procedures and data. For a computer, there is a memory, and there is a memory function to ensure proper operation. There are many types of memory, which can be divided into master memory and auxiliary memory, main memory, but also known as internal memory (referred to as memory), and secondary memory (abbreviation). Outline is usually a magnetic medium or a disc, like a hard disk, floppy disk, tape, CD, etc., can save information for a long time, and does not depend on electricity to save information, but is driven by mechanical components, the speed is slower than the CPU. The memory refers to the storage components on the motherboard. It is the direct communication between the CPU, and stores the components of the data, stores the data and programs currently being used (ie, the execution). Its physical substance is a group or more groups. The data input and data storage functions are integrated, and the memory is only used to temporarily store programs and data, and once the power is turned off, the program and data will be lost.
starts from a computer, there is memory. Memory development has also experienced many technological improvements today, from the earliest DRAM, to FPMDRAM, EDODRAM, SDRAM, etc., the speed of memory has been increased and capacity is also increasing. Today, what kind of memory is the server mainly? The server of the IA architecture is generally used in RegisteredecsDram.
Since the memory is used to store data and programs that are currently being used (ie, the execution), how do it work? The memory of the computer we usually refer is dynamic memory (ie DRAM). The so-called "dynamic" in dynamic memory is referred to. When we write data to DRAM, after a period of time, the data will be lost, so it needs An additional circuit performs memory refresh operations. The specific working process is such that a DRAM storage unit is stored 0 or 1 depends on whether the capacitor is charged, with a charge represents 1, no charge represents 0. But the time is long, the capacitor represents 1, the capacitor represents 0, the capacitor is absorbed, which is the cause of data loss. The refresh operation periodically checks the capacitance. If the amount of electricity is greater than the full power amount, it is considered to represent 1, and the capacitance is filled; if the amount of electricity is less than 1/2, it is considered to represent 0, and the capacitance is discharged. To maintain the continuity of the data.
Storage unit
Static storage unit (SRAM)
1) Storage principle: stored data by the trigger.
2) unit structure: six tube NMOS or OS configuration.
3) Advantages: fast speed, simple use, no need to refresh, very low static power consumption; often used as Cache.
4) Disadvantages: The number of components, low integration, and operational power consumption.
5) Common SRAM integrated chip: 6116 (2K × 8), 6264 (8k × 8), 62256 (32K × 8), 2114 (1K × 4).
Dynamic storage unit (DRAM)
1) Storage principle: The principle of the MOS pipe gate capacitor can store charge, need to refresh (early: three tube basic unit;) Single tube basic unit).
2) Refresh (regenerated): To make it to avoid the loss of the information to avoid storage, it must be set to the gate capacitance to supplement the charge.
3) Refresh time: Time to refresh regularly. This time must be less than the time (less than 2 ms) of the gate capacitance naturally hold information.
4) Advantages: The integration is much higher than SRAM, low power consumption, and the price is low.
5) Disadvantages: The peripheral circuit is complex due to the need to refresh; the refresh also makes the access speed are slower than SRAM, so in the computer, DRAM is often used to make the master memory.
Non this, since the structure of the DRAM memory cell is simple, the components used are less, the integration is high, and the power consumption is low, so that the mainstream product of the large capacity RAM has been used.
Other
Mobile phone we often see RAM4G RAM512M, we must not be misleaded, even if the ROM is big, but the RAM is small, or you can't play large games. The ROM is stored when storing what is used, and the RAM is a storage used when running a program. So when you purchase a phone, you must pay attention to this information.
RAM: An audio format, you can use thousands of listening to play. RA, RAM and RM are REAL's mature network audio format, which uses "audio stream" technology, so it is very suitable for webcasts. You can add copyright, singer, manufacturer, mail, and song name when making.
RA can be referred to as a multimedia propagation on the Internet, suitable for real-time playback on the network, is the best format of online music online music.
RAM: Role / Responsibilities Allocation Matrix, is a matrix formed by assigning each of the WBS (work decomposition structure) to the executive in the OBS (tissue decomposition structure), is human resources Management words.
Ram: Radar Absorbing Material Radar absorbing material refers to a material capable of reducing the target radar scattering section (RCS) by its own absorption.
RAM: Relative Atomic Mass relative to atomic mass (atomic quantity).