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Phase change memory (PCM) is a type of non-volatile RAM that stores data by changing the state of the material used, meaning it changes back and forth between amorphous and crystalline states on a microscopic level. PCM is considered an emerging technology.
PCM is 500 to 1,000 times faster than normal flash memory. PCM technology can also offer cost-effective, high-volume and high-density nonvolatile storage on an unparalleled scale.
Phase change memory is also known as perfect RAM, PCME, PRAM, PCRAM, ovonic unified memory, chalcogenide RAM and C-RAM.
In the amorphous state (or disordered phase), the material in PCM memory has high electrical resistance. In the crystalline state (or ordered phase), it has less resistance. Thus, electrical current is allowed to be turned on and off to represent digital high and low states.
This is one of several memory technologies competing to replace flash memory, which has a number of problems. Phase change memory can offer much higher performance where rapid writing is required. Flash memory also degrades with each burst of voltage. Phase change memory devices also degrade, but at a much slower rate. However, the lifetime of phase-change memory is limited by a tree-like data structure called generalized suffix tree, thermal expansion during programming, metal migration and other unknown mechanisms.
Also, unlike flash memory, PCM does not require a separate "erase" step when changing stored information from one to zero or zero to one. Thus, PCM is bit-alterable and much faster for both reading and writing data.
Several well-known organizations, such as the IBM, Intel, Samsung, etc., are conducting research into PCM technology. Some industry experts believe that PCM may be the data storage technology of the future, replacing hard drives with solid state drives.