Ram/rom Personal Understanding

1, what is Ram/rom

Ram:random Access memory, after the system power down, the data inside will be lost, such as the computer's memory bar.

Rom:read only Memory, the system can save data after power down.

2, Common RAM

SRAM static RAM (static RAM), currently the fastest RAM, is generally used as the CPU's first-level cache.
DRAM dynamic RAM, which is slower than SRAM, but much faster than ROM, the original computer's memory bar is DRAM. The so-called dynamic is because the DRAM data is lost and needs to be refreshed.
Sdram,ram of the improved type.

DDR RAM, an improved type of SDRAM, differs in that it can read and write two times in a single clock, so it is fast, and now most of the DDR3 of the memory bar is the DDR RAM, which has replaced the original DRAM.

3, Common ROM

PROM, programmable ROM (that is, you can write data in the ROM), one-time, can only be burned once, it is no longer necessary.

EPROM, can erase the programmable ROM, erase the original program by Ultraviolet Ray. A general-purpose memory.

EEPROM, through electronic erase, write time is long, very slow.

4, what is Flash

Flash is also called flash memory. The combination of EEPROM can be electronic erase and RAM fast read and write a bit. It is fast and can be saved without power. Both USB and MP3 are flash.

The original embedded domain, generally used ROM (EPROM) as a storage medium, but now has a full use of flash.

5, Common Flash

Nor flash nor flash and SDRAM read the same way, so you can directly run the inside of the code, which can reduce the size of the SRAM and cost savings.

NAND flash, without the use of random read technology, he reads a piece generally is 512 bytes, this is relatively inexpensive, but so the CPU can not directly run the NAND flash code. So a lot of development boards that use NAND flash use a small nor flash to run the startup code in addition to NAND flash.

Ram/rom Personal Understanding