Differences between Rom, Ram, DRAM, SRAM, and Flash

ROM and RAM are both semiconductor Memory, ROM is short for Read Only Memory, and RAM is short for Random Access Memory. ROM can still maintain data when the system stops power supply, while RAM usually loses data after power loss. A typical RAM is the computer memory. RAM has two categories: Static RAM (Static RAM/SRAM). The speed of SRAM is very fast. It is the fastest storage device for reading and writing, but it is also very expensive, therefore, it can only be used in demanding scenarios, such as CPU Level 1 buffering and level 2 buffering. The other is Dynamic RAM (Dynamic RAM/DRAM). DRAM retains data for a short period of time and is slower than SRAM, but it is faster than any ROM, but in terms of price, DRAM is much cheaper than SRAM, and computer memory is DRAM. DRAM is divided into many types. Common types include FPRAM/FastPage, EDORAM, SDRAM, ddr ram, RDRAM, SGRAM, and WRAM. Here we will introduce a ddr ram. Ddr ram (Date-Rate RAM) is also called ddr sdram. The improved RAM is basically the same as that of SDRAM. The difference is that it can read and write data twice at a clock, this doubles the data transmission speed. This is the most widely used memory in computers, and it has a cost advantage. In fact, it beat Intel's other memory standard-Rambus DRAM. In many high-end graphics cards, high-speed ddr ram is also provided to increase the bandwidth, which can greatly improve the pixel rendering capability of the 3D accelerator card. There are also many types of ROM. The difference between the PROM and the EPROM is that the PROM is one-time, that is, after the software is filled in, it cannot be modified. This is an early product and cannot be used now. The EPROM is used to erase the original program through ultraviolet radiation and is a general memory. Another type of EEPROM is an electronic interface. It has a high price, a long write time, and a low write speed. For example, the mobile phone software is usually placed in the EEPROM. When we call, some of the last dialing numbers are temporarily stored in the SRAM, rather than writing the pass record immediately (the call record is stored in the EEPROM ), at that time, there was a lot of important work (CALLS) to do. If you write data, a long wait would be unbearable for users. FLASH Memory, also known as FLASH memory, combines the strengths of ROM and RAM, not only has the electronic Erasable Programmable (EEPROM) performance, data will not be lost after power failure, and data can be quickly read (NVRAM advantage), which is used in USB flash drives and MP3. In the past 20 years, embedded systems have been using ROM (EPROM) as their storage devices. However, in recent years, Flash has completely replaced the position of ROM (EPROM) in embedded systems, it is used to store Bootloader, operating system or program code, or directly used as a hard disk (USB flash disk ). Currently, there are two types of Flash: NOR Flash and NADN Flash. The reading of NOR Flash is the same as that of our common SDRAM. Users can directly run the code loaded in nor flash, which can reduce the capacity of SRAM and save costs. NAND Flash does not adopt the random read Technology of memory. It reads 512 bytes at a time, usually in a low cost. Users cannot directly run NAND Flash code. Therefore, many development boards that use NAND Flash use not only NAND Flah, but also a small NOR Flash to run the startup code. NOR Flash is usually used for small capacity. Because of its fast reading speed, it is used to store important information such as the operating system, while nand flash is used for large capacity, the most common nand flash application is the DOC (Disk On Chip) used in the embedded system and the "FLASH Disk" we usually use, which can be erased online. FLASH on the market is mainly from Intel, AMD, Fujitsu and toshba, while the main manufacturers of NAND Flash are Samsung and toshba.