Non-volatile random-access memory: Difference between revisions

Revision as of 17:32, 13 February 2024

Revision as of 23:57, 13 February 2024

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==Early NVRAMs==

Some early computers used [[Drum memory|magnetic drum]] which was non-volatile as a byproduct of its construction. The industry moved to [[magnetic-core memory]] in the later 1950's1950s, which stored data in the polarity of small magnets. Since the magnets held their state even with the power removed, core memory was also non-volatile. Other memory types required constant power to retain data, such as [[vacuum tube]] or solid-state [[Flip-flop (electronics)|flip-flop]]s, [[Williams tube]], and semiconductor memory (static or dynamic RAM).

Advances in [[semiconductor fabrication]] in the 1970s led to a new generation of [[Solid state (electronics)|solid state]] memories that magnetic-core memory could not match on cost or density. Today dynamic RAM forms the vast majority of a typical computer's [[main memory]]. Many systems require at least some non-volatile memory. Desktop computers require permanent storage of the instructions required to load the operating system. Embedded systems, such as an engine control computer for a car, must retain their instructions when power is removed. Many systems used a combination of RAM and some form of ROM for these roles.