A team of researchers at IBM Zurich have come up with a way to utilize PCM as a simple computational device which does not follow the traditional Von Neumann architecture.  Phase change memory works in a way somewhat analogous to optical storage, with changes to the physical state of the storage medium being used to represent a 1 or 0.  In this case it is a substance that switches from amorphous to crystalline and back again with the application of electrical current; the article at The Register describes this in more detail

This research envisions connecting to a sensor which can send an electrical pulse to PCM to change its state; the example given involves detecting rain and changing the memory to a 1 if rain is detected, a 0 if not. With the application of a algorithm to detect the state of the PCM you can read out rainfall patterns from storage without requiring a processor.  While the computational power of PCM will be quite simple, describing how this works is certainly not so follow the links to the research if your curiosity is piqued.

"But memory has no processor so some aspect of a memory device has to be used, an aspect that changes its nature depending upon the data contents of the memory device. Also the computation is going to be quite primitive"

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