In recent years, nonvolatile memory (NVM) technology has developed rapidly. Non-volatile memory is mainly divided into two types: block addressing and byte addressing. Block addressing non-volatile memory represented by flash memory (flash memory) has been widely used in embedded systems, desktop systems, and data centers. Byte-addressed non-volatile memory mainly includes phase change memory (PCM), resistive random-access memory (RRAM), spin-transfer torque memory (STT-RAM), etc. In terms of byte-addressable non-volatile storage technology, NVDIMM is an analog persistent memory storage device that has been commercially available. NVDIMM uses a hybrid form of flash memory and DRAM (Dynamic Random Access Memory), and uses capacitors or back-up power supplies to ensure that DRAM data is not lost after power failure to simulate persistent memory.

In the write operation procedures of many storage systems, the memory serves as an important bridge between the controller and the hard disk to provide faster performance. However, if a sudden power failure occurs, how to protect the data in the memory from loss? This is the storage system. The usual topic. Volatile memory means that when the computer is shut down or the computer is shut down suddenly or accidentally, the data in it will be lost, just like memory. Non-volatile memory will not lose data under the above conditions, such as external storage such as hard disks. This article introduces the difference between non-volatile memory and volatile memory in detail.

1. What is non-volatile memory

1.1 Definition

"Non-Volatile Memory (NVMe) is a semiconductor technology that does not require continuous power supply to retain data or program codes stored in computing devices. System manufacturers use different types of non-volatile memory chips for various purposes. For example, one type of NVM may store controller program codes for devices such as hard disk drives (HDD) and tape drives. Another type of NVM is commonly used for data storage in solid state drives (SSD), USB drives, and memory cards in digital cameras, mobile phones, and other devices.

Solid-state storage generally uses a variant of non-volatile memory called NAND flash memory. SSDs have no moving parts. They have higher performance than mechanically addressed HDDs and magnetic tapes, which use magnetic heads to read and write data to magnetic storage media. An SSD directly connected to a computer processor via a PCIExpress (PCIe) bus provides lower latency than a Serial Attached SCSI (SAS) or Serial Advanced Technology Attachment (SATA)-based SSD inserted into an external drive bay.

1.2 Type

(1) Programmable read-only memory: Programmable read-only memory PROM (Programmableread-onlymemory) has a determinant screw inside, which can be burned by current according to the needs of the user (manufacturer) to write to the required The data and programs of the data cannot be recovered once the screw is burned, that is, the data cannot be changed.

(2) Electrically Erasable Programmable Read Only Memory (Electrically Erasable Programmable Read Only Memory) (Electrically Erasable Programmable Read Only Memory) The operating principle of EEPROM (Electrically Erasable Programmable Read Only Memory) is similar to EPROM, but the method of erasing is It is done using a high electric field, so there is no need for a transparent window.

(3) Erasable programmable read-only memory: EPROM (Erasableprogrammablereadonlymemory) can use high voltage to program and write data, but the line needs to be exposed to ultraviolet light for a period of time before the data can be erased Empty it out and reuse it again. Therefore, a transparent window made of quartz glass is reserved on the package shell for ultraviolet exposure.

(4) Electrically alterable read-only memory: EAROM (Electrically alterable readonly memory) uses the same chip and writing principle as EPROM, but in order to save costs, there is no transparent window on the package, so it cannot be programmed after writing Erase and rewrite.

(5) Flash memory: Flash memory (Flash memory) is a form of electronically erasable programmable read-only memory that allows memory to be erased or written multiple times during operation. This technology is mainly used for general data storage, as well as the exchange and transmission of data between computers and other digital products, such as memory cards and U disks. Flash memory is a special kind of EEPROM that is erased with macro blocks. The early flash memory erased the data on the entire chip once.

2. What is volatile memory

RAM (RandomAccessMemory) is the full name of random access memory, which is equivalent to the mobile storage on the PC, used to store and save data.

It can be read and written at any time. RAM is usually used as a temporary storage medium for the operating system or other running programs (it can be called system memory). However, RAM cannot retain data when the power is turned off. If you need to save data, you must write them into a long-term storage (such as a hard disk). Because of this, RAM is sometimes referred to as "variable memory." RAM memory can be further divided into two categories: static RAM (SRAM) and dynamic memory (DRAM). DRAM is widely used as the main memory of the system because of its low price per unit capacity.

3. The difference between non-volatile memory and volatile memory

Volatile memory is a semiconductor technology that requires continuous power supply to retain stored data. Prominent examples of volatile memory are static random access memory (SRAM) and dynamic RAM (DRAM). Manufacturers sometimes add battery power to volatile storage devices to support persistent data storage.

Enterprise and client computer systems usually use a combination of volatile and non-volatile memory technologies, and each type of memory has its advantages and disadvantages.

For example, SRAM is faster than DRAM and is very suitable for high-speed caching. DRAM is the successor of SRAM. Compared with SRAM in active mode, its production cost is lower and the required power is lower. A common use case of DRAM is to store the main program code required for the operation of a computer processor.

Non-volatile NAND flash memory is slower than DRAM and SRAM in writing and reading data. However, the production cost of NAND flash memory is much lower than that of DRAM and SRAM, which makes the technology more suitable for persistent data storage in enterprise systems and consumer devices. Non-volatile memory and non-volatile memory expression (NVMe) sound similar, but their meanings are different and different. NVM is a semiconductor technology that appeared in the late 1940s, and NVMe is a host controller interface and storage protocol, which was developed in 2009 by the Alliance of Technology Suppliers.

The NVM host controller interface working group released the 1.0 NVMe specification on March 1, 2011. NVMe aims to accelerate the data transfer between the host system and the SSD through the PCIe bus of the computer. NVMe supports the use of different types of non-volatile memory, such as NAND flash memory and the 3DXPoint technology developed by Intel and Micron. NVMe is an alternative to the Small Computer System Interface (SCSI) standard and Advanced Technology Attachment (ATA) standard for SAS and SATA drives, respectively. The number of CPU instructions used by NVMe is less than half of the SCSI and ATA command sets. Compared with SSD based on SAS and SATA, PCIeSSD based on NVMe has lower latency, higher IOPS and lower power consumption.

The above is the introduction of the difference between non-volatile memory and volatile memory. In the case that volatile memory requires power to retain its information, the source of non-volatile memory is not needed. If the power of the volatile memory is turned off, the information in the volatile memory will be quickly deleted. If the power of the non-volatile memory is turned off, the non-volatile memory retains its information. Volatile memory is often used because it is faster and more suitable for retaining sensitive information, because the information can be quickly deleted by turning off the power. Random access memory or RAM is a type of volatile memory. RAM is used to temporarily store data needed to run programs and applications on electronic devices. Non-volatile memory is used because it is more suitable for long-term retention of information.

Summarized by Easybom.