IBM has found a better way of using an optical memory format with several advantages over conventional formats. It’s worked out how to store 3-bits of data per cell in phase change memory.
The format works in a similar way to Blu-Ray discs, namely by manipulating glass. Passing a high current through the glass can switch it back and forth between a crystalline (structured) and amorphous (unstructured) state. Applying a low voltage can then read the state of the glass.
Using individual cells of the glass and designating the amorphous state as a 0 and the crystalline state as a 1 means you can use it for digital storage. Unlike traditional RAM, this technology doesn’t lose the data when the power is cut. And compared with flash memory, it’s considerably faster and more durable, theoretically lasting for millions of write cycles.
The big limitation so far has been that when storing one bit per cell, phase change memory works out to be both more expensive and physically larger than flash memory of the same storage capacity, meaning it hasn’t really been viable for portable devices.
IBM’s solution is applying high temperatures to the cells, which allows for more than two measurable states. To date this has been a tricky approach because the measurements for these states have drifted as the ambient temperature fluctuates, making long-term storage unreliable.
According to IBM, it’s now found a way to keep track of this drift and thus continue to correctly read the designated state regardless of temperature changes. In a test it successfully maintained a 3-bit per cell storage for one million read/write cycles.
Switching to a 3-bit setup means storing four times as much data in the same physical size of phase change memory unit (or the same amount of data in a quarter of the space.) IBM suggests several uses for the technology including using it to store online databases that need to handle fast queries such as in financial transactions, and storing a phone’s operating system to allow much faster startups.
(Image credit: IBM)