Flash storage is not as fast as the main memory (RAM); but RAM can't be used to store your regular files because of its volatile nature (and also because it's expensive). It appears we may soon have the perfect middle ground of the two. Scientists at IBM have demonstrated reliably storing 3 bits of data per cell using a relatively new memory technology known as phase-change memory (PCM). Engadget reports: To store PCM data on a Blu-ray disk, you apply a high current to amorphous (non-crystalline) glass materials, transforming them into a more conductive crystal form. To read it back, you apply a lower voltage to measure conductivity -- when it's high, the state is "1," and when it's low, it's "0." By heating up the materials, more states can be stored, but the problem is that the crystals can "drift" depending on the ambient temperature. IBM's team figured out how to track and encode those variations, allowing them to reliably read 3-bits of data per cell long after it was written. That suddenly makes PCM a lot more interesting -- its speed is currently much better than flash, but the costs are as high as RAM thanks to the low density.