The battle over the next storage technology is heating up. IBM scientists this week demonstrated a working practical version of their Multi-bit Phase Change Memory. PCM combines speed, endurance, non-volatility and density into a single chip. This is Flash memory part 2 and may be the first technology to threaten hard drives. 100 times faster than flash with read/write durability of 10 million cycles this is what Flash always wanted to be. PCM is the little prince who one day may become the king of storage.
IBM developed a 200,000 memory cell test chip to prove the technology. The chip was developed using older 90nm CMOS fabricating technology – Intel is just about to start using 22nm technology – , the cells consists of an alloy between two electrodes, top and bottom. When voltage is passed between the electrodes the alloy heats up and changes once it hits the right temperature. This change in structure affects its electrical resistance and this is used to represent 1’s and 0’s. The alloy itself belongs to a class of materials called chalcogenide compounds, materials that change their internal structure from crystalline to amphoras under certain circumstances. DVD-R disks use a similar material but they use light to read and write, changing the refractive index.
Dr. Haris Pozidis, Manager of Memory and Probe Technologies at IBM Research – Zurich. “By demonstrating a multi-bit phase-change memory technology which achieves for the first time reliability levels akin to those required for enterprise applications, we made a big step towards enabling practical memory devices based on multi-bit PCM.”
PCM technology has many advantages over current Flash memory – NVRAM, Non-Volatile Random Access Memory -, write speeds are a hundred times quicker, read and write cycles in the millions instead of thousands. There was how-ever one major problem for IBM to over come with PCM, drift. Early PCM systems after time would stop reading correctly, the cells resistance would drift. This was caused by the alloy not completely changing states, with just an edge or corner being enough to start drift. Each additional cycle would add to the amount of confused material eventually making the cell un-usable. To correct this IBM developed a multiple cycle write that writes and checks all material has changed state, applying more voltage if required. With a clever system to improve reliability IBM was also able to increase the useable memory by creating multi-bit technology. By storing 4bit’s per memory cell IBM is able to match and beat Flash’s memory density – the amount of memory per flash chip -.
PCM technology was first discovered in the 60’s by Stanford R. Ovshinsky who first began experimenting with chalcogenide glasses as a form of memory technology. In 1970 Gordon Moore – Intel founder – wrote a paper for Electronics magazine on the early technology. Material quality and power requirements limited its commercial potential. Reading and writing to each cell was like firing up an arc welder and the material often exploded as it was heated to much. While this early work wasn’t an instant commercial success it did create the technology behind CD-R and DVD-R and is the basis of all PCM technology today, with IBM’s announcement PCM has made a comeback.
The only advantage that mechanical hard-drives have over solid state memory storage is dollars per megabytes cost. While a 500GB hard drive costs $30 an SSD of that capacity will cost $1500. For solid state storage to compete it is going to have to get cheaper, much cheaper.
IBM’s demonstration is a breakthrough but it isn’t the only technology vying for the throne, there are other contenders for the Storage King crown. MRAM uses a magnetism to store bits in positive or negative nature of a magnetic field. NanoRAM uses carbon nanotubes as a storage medium, offering potentially huge data densities. IBM’s millipede technology is like a nano sized punch-card technology.
Hard drives should be starting to get a little concerned about now, they’ve had a good run and served us well but new technology is approaching that will take over its role as the mass storage type of choice for the PC industry. IBM’s scientists from around the world teamed up for these advancements, proof that when we put our heads together we can solve some really very tricky problems.
More information at IBM’s Press Release
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