Computers based on the classical von Neumann architecture process data using the CPU, while the raw data and results of calculations are stored elsewhere – in main memory, on a hard disk or a solid-state drive. This architecture has been in use for several decades, but it is by no means optimal and efficient due to the presence of so-called bottlenecks.
The most famous bottleneck limiting the performance of modern computers is the interface between the processor and memory, this bus has a limited bandwidth, and at times of high computational load processors are forced to “wind idle loops”, losing time and waiting for the release of the bus. This disadvantage is completely devoid of the most powerful computer of natural origin – the brain, consisting of neurons capable of simultaneously storing and processing information.
In recent years, scientists and engineers have made quite significant progress in mimicking the functioning of the brain, using a “memory-computing” architecture implemented on the basis of memristor cells. These cells, like neurons, are also capable of storing and processing information, which frees such processors from the constant need to move data, which consumes quite a lot of time and energy.
And not so long ago, scientists from the Swiss Ecole Polytechnique Federale de Lausanne (EPFL) developed and produced a prototype of a new processor, in which the “calculations in memory” architecture is implemented using an entirely new approach. And the basis for all this was a conventionally two-dimensional material – molybdenum disulfide (molybdenite, MoS2), which has long appeared in the role of one of the most basic alternative materials for electronics.
A single layer of molybdenite is only three atoms thick. This material is an excellent semiconductor and has enormous potential for the miniaturization of electronic devices and the components in which it is used.
The new processor is based not on memristors, but on so-called floating-gate field-effect transistors (FGFETs). These transistors, capable of storing electrical charge over long periods of time, are already widely used in non-volatile flash memory, which can be found in every computer, cell phone, camera, and camcorder. The molybdenum disulfide cells are sensitive to electrical charges stored in FGFET transistors, and because of this they can perform the function of storing and logical information processing simultaneously.
“We were holding the first experimental chip with this kind of memory-logic cell ten years ago,” says Andras Kis, the lead researcher. “Now we can already make a circuit with up to 80 such cells in one run and they have a set of strictly defined parameters. This opens the way to smaller computing devices with high computational power and the highest energy efficiency.