IBM has achieved a breakthrough that could dramatically expand the applications for Phase-Change Memory (PCM) storage. This optical storage technology has already been used in Blue-ray disks and elsewhere for the last 15 years. It is faster and more durable than flash, and unlike DRAM, it doesn’t lose data when it is turned off. Despite these benefits, PCM usage has been limited by its cost and storage density. But now IBM researchers have dramatically increased the capacity, making it a fast and easy storage solution that could support the growing data demands for mobile devices and the Internet of Things.
The benefit over flash is clear: PCM can read data in less than one microsecond, while flash takes 70 microseconds. It can also endure more than ten million write cycles, while flash only lasts 3,000 cycles. RAM is still faster, but in certain applications PCM could provide universal storage, replacing both RAM and flash.
PCM works by using materials that exhibit two stable states, the amorphous (with low electrical conductivity) and crystalline (highly conductive) phases. To store bits (a “0” or a “1”), on a PCM cell, a high or medium electrical current is applied to the material. To read the bit back, a low voltage is applied. The challenge is that the crystals have a tendency to “drift,” which affects the stability of the cell’s electrical conductivity over time. The IBM researchers developed a way to track and encode the drift variations, which allowed them to reliably read 3-bits of data per cell—smashing the previous record high of 1-bit per cell in a PCM. They demonstrated their breakthrough at the IEEE International Memory Workshop in Paris on May 17.
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