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salvationdata.jessie · Joined: 26 Nov 2007 Posts: 11 Location: China

In computer industry, there are three kinds of semiconductor memorizer mostly used.
EEPROM（Electrically Erasable Programmable Read Only Memory）used to save BIOS information. Data can be kept after power off, in recent years, the flash RAM used to save BIOS information is also one kind of EEPROM.
The DRAM（Dynamic Random Access Memory）is used to save temporary data, the data can be kept only by being kept refreshing. The data stored in the chip will be gone when power off.
The SRAM（Static Random Access Memory）is used to save the common instruction and data of the CPU. The data can be kept without being refreshed, but the data stored in the chip will be gone when power off.
Usually, we call the semiconductor memorizer that can keep data after power off “NVM” (Non-Volatile Memory), and Memorizer like DRAM, SRAM is called VRAM.
As the semiconductor memorizer used in HITACHI HDD can access data randomly, it is called NVRAM (Non-Volatile Random Access Memory).