Don't make computers seek out data. Make the data move to where it can be used.
That, roughly, is one way to describe the racetrack memory concept, which IBM argues could one day lead to memory that could hold 100 times more data than flash memory does today and cost 100 times less. So that 2GB card you bought for $20 this week would hold 200GB, or more than a lot of notebook hard drives, and cost 20 cents.
In racetrack memory, information is stored in the domain walls, or boundaries, between magnetic regions on a wire. The domain walls are then shuttled up or down the wire via electrical pulses toward another component that can interpret whether the domain wall represents a "1" or a "0."
"We have a series of zeros and ones, and our objective is to shift that information to and fro without upsetting it," said Stuart Parkin, an IBM fellow, in an interview. Parkin is one of the authors of a paper on the subject being published in the April 11 edition of Science. "Unlike a hard drive, we have no moving parts. We have no moving atoms. We just have magnetic moments."
In flash memory and hard drives, data lives in a discrete location and a computer (or hard drive head) finds it. Shuttling the bits on a wire opens up the possibility for making 3D memory, and hence more dense memory, because wires could be stacked on top of each other. The time it takes to record or retrieve data could also be reduced.
Racetrack chips, potentially, could additionally last far longer because they have no moving parts, unlike hard drives, and won't get progressively worn out by successive read-erase cycles like flash memory. Flash chips typically last 100,000 read-write cycles before errors can become a problematic possibility.
The paper in detail describes how they were able to create, move, and interpret domain walls on horizontal permalloy nanowires.
One of the big breakthroughs in IBM's approach, said Parkin, is the fact that the domain walls are moved with electrical current. In the past, scientists tried to move domain walls in this manner with magnetic fields. That created two problems. One, using magnetic fields takes far more energy. Second, the magnetic fields can disturb adjacent magnetic fields, thereby potentially corrupting data.
"We spent about three years together on this. Three or four years ago, people hadn't even demonstrated moving one domain wall with small bursts of current," Parkin said. "It is an understanding of how the magnetic fields work together with building the nanowires in such a way that the domain walls can move smoothly along these wires without getting stuck on small perturbations."
Parkin is a leading figure in magnetic storage research. His work on thin magnetic film structures allowed IBM, among others, to exploit the giant magnetoresistive effect to significantly boost the density of hard drives.
In the next two to four years, IBM hopes to create a complete, working prototype of a racetrack chip with an integrated device that can read the data shuttling across the wire, said Parkin. In 7 to 10 years, chips like this, conceivably, could start coming out of factories. IBM doesn't make memory chips, but is interested in coming up with ideas and inventions in the area it can subsequently license.
It's all about data storage
If the semiconductor market revolved around processors in the 1990s, you can make a good argument that it's going to revolve around data storage in the next decade. The growth of the Internet and digital media has lead to the need for chips, software, and systems that can help store--and then find and retrieve--terabytes and exabytes of data. (An exabyte is a quintillion bytes, or a billion gigabytes.)
"The problems we're looking at aren't computationally driven, per se, but more information management problems," Mark Dean, an IBM fellow and director of the Almaden Research Center, said in an interview in February. "Computation is not the hard part anymore."
In the memory world, several companies are touting approaches for replacing existing technologies. Earlier this month, for instance, Numonyx--a joint venture between STMicroelectronics and Intel--said that it will later this year begin to commercially ship phase change memory (PCM), a type of dense memory that scientists have experimented with in labs for decades.
Start-up Grandis, as well as IBM, meanwhile, are examining spin transfer torque memory (STT RAM), which operates on similar principles as racetrack memory, while Zettacore is trying to store data with designer molecules. (IBM also has a lab project under way in which DNA could be used to organize carbon nanotubes into grids for data storage.)
Traditional approaches, of course, aren't giving up easily. Toshiba discussed a technique for building 3D flash chips. SanDisk acquired a line of 3D read-only memory flash chips when it bought Matrix Semiconductor, and is working on chips that can read, erase, and rewrite data.
In the hard drive world, Seagate will try to increase density on drives with a heating technology, while Hitachi is pursuing patterned media hard drives.