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IBM creates artificial neurons from phase change memory for cognitive computing

Lucas Mearian | Aug. 4, 2016
The artificial neurons can sustain billions of switching cycles, which means multiple years of operation

Phase Change Memory neuron
IBM Research

A depiction of a phase-change neuron and the two states it exists in: crystaline (ordered) and amorphous (random).

Neurologic processors could offload data-intensive workloads

The artificial neurons would be used to create neurologic processors that could reside side-by-side and compliment standard processors, offloading analytics-intensive workloads, according to Tuma.

"We show we can have both synapses and neurons using phase change cells," Tuma said. "The discovery is important in taking phase change memory to the next level and to use it for computations."

PCM, which is also known as phase-change random access memory (PRAM) is a form of nonvolatile memory based on using electrical charges to change areas on a glassy material from crystalline, or an ordered, state to amorphous state, where its atoms are randomly distributed.

By applying spikes of voltage, the PCM's state can be switched back and forth, which can be used to represent ones and zeros or bits of data. PCM, however, can exist in more than two states, not just zeros and ones.

Companies such as IBM, Micron, Samsung and Everspin have been experimenting with PCM as a type of non-volatile memory because it offers up to 100 times the performance and vastly better endurance over NAND flash. Because it is expensive to make, to date it has yet to see significant market uptake. PCM also doesn't suffer the data corruption issues associated with NAND flash that stores multiple bits per cell.

However, the latest research is not associated with creating a new non-volatile memory. Instead, PCM is being used to create a new type of processor.

"We have been researching phase-change materials for memory applications for over a decade, and our progress in the past 24 months has been remarkable," said IBM Fellow Evangelos Eleftheriou. "In this period, we have discovered and published new memory techniques, including projected memory, stored 3 bits per cell in phase-change memory for the first time, and now are demonstrating the powerful capabilities of phase-change-based artificial neurons."

The artificial neurons consist of phase-change materials, including germanium, antimony and telluride. The materials are the basis of re-writable Blue-ray discs today. However, the artificial neurons do not store digital information; they are analog, just like the synapses and neurons in our brain.

In the published demonstration, the team applied a series of electrical pulses to the artificial neurons, which resulted in the progressive crystallization of the phase-change material, ultimately causing the neuron to fire. In neuroscience, this function is known as the integrate-and-fire property of biological neurons. This is the foundation for event-based computation and, in principle, is similar to how our brain triggers a response when we touch something hot.

 

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