New method may lead to faster, smaller computers

Faster, smaller, greener computers, capable of processing information up to 1,000 times quicker than currently available models, could be made possible by replacing silicon with phase-change materials, according to a new study.
Researchers found that the present size and speed limitations of computer processors and memory could be overcome by replacing silicon with 'phase-change materials' (PCMs).
PCMs are capable of reversibly switching between two structural phases with different electrical states - one crystalline and conducting and the other glassy and insulating - in billionths of a second.
Modelling and tests of PCM-based devices showed that logic-processing operations can be performed in non-volatile memory cells using particular combinations of ultra-short voltage pulses, which is not possible with silicon-based devices.

In these new devices, logic operations and memory are co-located, rather than separated, as they are in silicon-based computers.
These materials could eventually enable processing speeds between 500 and 1,000 times faster than the current average laptop computer, while using less energy.

The processors, designed by researchers from the University of Cambridge, the Singapore A STAR Data-Storage Institute and the Singapore University of Technology and Design, use a type of PCM based on a chalcogenide glass, which can be melted and recrystallised in as little as half a nanosecond using appropriate voltage pulses.
The calculations performed by most computers, mobile phones and tablets are carried out by silicon-based logic devices.

"However, as demand for faster computers continues to increase, we are rapidly reaching the limits of silicon's capabilities," said Professor Stephen Elliott of Cambridge's Department of Chemistry, who led the research.
The method of increasing the power of computers has been to increase the number of logic devices which they contain by progressively reducing the size of the devices.
An alternative for increasing processing speed without increasing the number of logic devices is to increase the number of calculations which each device can perform, which is not possible using silicon, but the researchers have demonstrated that multiple calculations are possible for PCM logic/memory devices.

The PCM devices recently demonstrated to perform in-memory logic do have shortcomings: currently, they do not perform calculations at the same speeds as silicon, and they exhibit a lack of stability in the starting amorphous phase.
However, the Cambridge and Singapore researchers found that, by performing the logic-operation process in reverse - starting from the crystalline phase and then melting the PCMs in the cells to perform the logic operations - the materials are both much more stable and capable of performing operations much faster.