If measured by patents, IBM are one of the most innovative businesses on the planet. When the annual patent filing results are released, IBM are usually sitting in the top handful of technology businesses being awarded with plenty of patents. Some of this work is via IBM Research, the division tasked with experimental technologies, which has existed for seven decades. Indeed, IBM Research has twelve laboratories across the world and more than three thousand researchers. Over the years, their scientists have acquired six Nobel Laureates, 10 U.S. National Medals of Technology, five U.S. National Medals of Science, six Turing Awards, 19 inductees in the U.S. National Academy of Sciences and 20 inductees into the U.S. National Inventors Hall of Fame.
Earlier this week, IBM demonstrated a way of storing 3 bits per data cell rather than the more traditional 2 bits. This used a new memory technology called phase-change memory, or PCM. Phase-change memory has caught the attention of manufacturers all over the world in recent years as it has the potential to replace DRAM. There are several advantages - PCM modules offer higher performance (both in reduced latency and transfer rates), greater longevity, are physically smaller and are non-volatile, so they don't lose their contents when the device runs out of power. To quantify the improved longevity, current PCM modules are able to be written to at least ten million times, compared with a typical USB flash drive, which will take three thousand write cycles.
PCM technology works because the materials in use have two stable states. There's the amorphous state, that is without a clearly defined structure, and the crystalline (structured) phase. The amorphous state shows low electrical conductivity whereas the crystalline shape is highly conductive. Applying a 0 or 1 bit to a PCM cell involves transmitting a high or medium current to the cell. The memory is read back by applying a lower current. Until IBM's announcement, companies had demonstrated storing one bit per cell but IBM's advances showed the technology storing three bits per cell. The demonstration used a sixty four thousand cell array kept at elevated temperatures and after a million memory endurance cycles. The advantage to three bits per cell is that it reduces the cost of the PCM modules bringing them closer to flash and cheaper than DRAM. IBM used some clever sounding technologies to store three bits per cell: "a set of drift-immune cell-state metrics" and "drift-tolerant coding and detection schemes." These technologies measure the physical properties of the PCM cell, as these things change over different temperatures and with time. IBM's system adapts the cell current thresholds to ensure reliability.
IBM believe that phase-change memory should be capable of providing "fast and easy storage to capture the exponential growth of data from mobile devices and the Internet of Things." Fortunately, IBM have expanded upon this broad, sweeping statement! The research team see the potential for a number of applications, such as a hybrid DRAM and PCM combination that uses PCM as an extremely fast cache. For enterprise customers and data centre operators, databases could be stored on PCM modules to accelerate performance and improve component reliability. And of course for our devices, using PCM to replace DRAM would offer improvements across the board. Faster RAM transfer speeds will also improve how quickly machine learning algorithms can process data, which in turns means we may see greater advances in artificial intelligence systems. IBM also alluded that thanks to the cost reduction, PCM should now be a viable component for smartphones, meaning we could soon have significantly quicker and more reliable internal memory. For more information on the technology, you can check out IBM's research video below.