NVRAM\FLASH\NVM的区别

 

  NVRAM\FLASH\NVM的区别

 

NVRAM（Non-Volatile Random Access Memory）： 非易失性随机访问存储器。电子设备能快速地访问该存储空间的内容（大多数情况下此类设备都是以字节方式地访问这些内容，并且掉电后也能保存它们）。有多种技术能实现这一策略，其中EEPROM是比较常见的。但是需注意的是：在手机设计中，通常用ROM的一个或两个扇区（实际上更多的情况下这个ROM就是FLASH）来模拟NVRAM，这样做的原因当然是节省花费了（因为ROM是必须的，而NVRAM则不一定）。

FLASH：是一种ROM（Read Only Memory），与其他ROM的不同在于半导体等级。注意：FLASH必须以扇区为单位访问，而NVRAM以字节为单位访问。这是NVRAM驱动必须实现一个算法（即一开始就复制一个扇区内的所有内容到RAM）的原因。

NVM：非易失性存储器。这是更普遍的概念，它涵盖了所有在掉电后仍能保持其内容的内存组件。在体系设计上这个技术是很有用的，它的技术详情此处省略。实际上，在一个工程中一个带有电池的DRAM（动态随机访问存储器）就能扮演NVM的角色，并且能很好地工作。

原文：

NVRAM: Non-Volatile RAM. The target is to have a electrical device that could be accessed quite fast, most of the time the content is calculated by bytes and the content could be saved after power down. There are different technical ways to implement this concept such as EEPROM which is very common. Please note, in mobile phone design, most of the time one or two sectors of ROM (most of the time it is FLASH) will be used to simulate NVRAM, the only reason is cost saving since ROM is a "must" but NVRAM is not.

FLASH: One kind of ROM and the difference to other ROM is semiconductor level. Please note, FLASH must be read/write by sectors but NVRAM should be read/write by bytes. It is why NVRAM driver have to implement an algorithm such as copying all the content in one sector to RAM first.

NVM: Non-volatie memory. It is more generic concept and covers all the memory components that could keeps its content after power off. It is useful during architecture design when the technical detail could be skipped. In fact, in one project, a DRAM with battery played as NVM and it worked quite good in that case.