Emerging Memories Poised to Explode

By Cadence

February 5, 2019

A couple of weeks ago was the Persistent Memory Summit. (For more details, see my post Persistent Memory.) Normally, this might be a minority-interest event, but the potential arrival of a new level in the memory/storage hierarchy means that everyone will (maybe) be affected. The generic name for this technology is PCRAM, or phase-change RAM. The memory works by heading the storage element, and either cooling it fast or slowly. If cooled slowly, the element ends up crystalline. If fast, then it ends up amorphous. These have different resistance, and so can store a bit. The non-generic name for the only currently commercialized technology in the space is 3DXpoint, and Intel has its own name, Optane. It is not quite the dream replacement for DRAM, since it is slower, but it is only 500ns versus 70-100ns, so it is close enough: compared to the processor's raw speed, even DRAM is really slow (200 cycles), so this is slower (say 1000 cycles) but still fast enough that the processor can stall while waiting for an access, and let the superscalar nature of the processor find some stuff to do in the meantime.

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