Sometimes a light touch is best: When you're telling a joke or hammering a tiny finishing nail into a wall, a gentle delivery often succeeds most effectively. Research at the National Institute of Standards and Technology (NIST) suggests it also may be true in the microscopic world of computer memory, where a team of scientists may have found that subtlety solves some of the issues with a novel memory switch.
This technology, resistive random access memory (RRAM), could form the basis of a better kind of nonvolatile computer memory, where data is retained even when the power is off. Nonvolatile memory is already familiar as the basis for flash memory in thumb drives, but flash technology has essentially reached its size and performance limits. For several years, the industry has been hunting for a replacement.
RRAM could surpass flash in many key respects: It is potentially faster and less energy-intensive. It also could pack far more memory into a given space—its switches are so small that a terabyte could be packed intoa space the size of a postage stamp. But RRAM has yet to be broadly commercialized because of technical hurdles that need addressing.
One hurdle is its variability. A practical memory switch needs two distinct states, representing either a one or a zero, and component designers need a predictable way to make the switch flip. Conventional memory switches flip reliably when they receive a pulse of electricity, but we're not there yet with RRAM switches, which are still flighty.
"You can tell them to flip and they won't," said NIST guest researcher David Nminibapiel. "The amount needed to flip one this time may not be enough the next time around, but if you use too much energy and overshoot it, you can make the variability problem even worse. And even if you flip it successfully, the two memory states can overlap,making it unclear whether the switch has a one or a zero stored."
This randomness cuts into the technology's advantages, but in two recent papers, the research team has found a potential solution. The key lies in controlling the energy delivered to the switch by using multiple, short pulses instead of one long pulse.