Researchers at UCLA’s Henry Samueli School of Engineering and Applied Science have found a way to improve computer memory, making it faster and 10 to 1,000 times more energy-efficient, by using electric voltage instead of a flowing electric current.
The ultra-fast, high-capacity class of computer memory is known as magnetoresistive random access memory, or MRAM. The UCLA team says its improved memory, called MeRAM for magnetoelectric random access memory, has potential to be used in future memory chips for smart-phones, tablets, computers and microprocessors, as well as for data storage, like the solid-state disks used in computers and large data centers.
The engineers say MeRAM’s key advantage over existing technologies is that it combines low energy with high-density, high-speed reading and writing times, and non-volatility — the ability to retain data when no power is applied, similar to hard disk drives and flash memory sticks, but MeRAM is faster.
Currently, magnetic memory is based on spin-transfer torque (STT) technology, which uses the magnetic property of electrons — referred to as spin — in addition to their charge. STT utilizes an electric current to move electrons to write data into the memory.
STT’s electric current–based write mechanism requires a certain amount of power, which means that it generates heat when data is written into it. In addition, its memory capacity is limited by how close to each other bits of data can be physically placed, a process which itself is limited by the currents required to write information.
The low-bit capacity, in turn, translates into a relatively large cost per bit, limiting STT’s range of applications.
With MeRAM, the UCLA team has replaced STT’s electric current with voltage to write data into the memory. This eliminates the need to move large numbers of electrons through wires and instead uses voltage — the difference in electrical potential — to switch the magnetic bits and write information into the memory.
This means the computer memory generates much less heat, making it more energy-efficient. And the memory can be more than five-times as dense, with more bits of information stored in the same physical area, which also brings down the cost per bit.
The research team was led by principal investigator Kang L. Wang, UCLA’s Raytheon Professor of Electrical Engineering, and included lead author Juan G. Alzate, an electrical engineering graduate student, and Pedram Khalili, a research associate in electrical engineering and project manager for the UCLA–DARPA research programs in non-volatile logic.
The work was supported by the Defense Advanced Research Projects Agency (DARPA) NV Logic Program. Other authors included researchers from the UCLA Department of Electrical Engineering, UC Irvine’s Department of Physics and Astronomy, Hitachi Global Storage Technologies (a Western Digital Company) and Germany’s Singulus Technologies.
In related news, the Super-efficient Equipment and Appliance Deployment (SEAD) Initiative — an international coalition of national energy agencies — has created a competition aimed at improving energy efficiency of computer monitors. Computer monitors can account for 35 percent or more of a desktop computer’s energy consumption. Globally, displays account for 30 to 40 terawatt-hours (TWh) of electricity consumption each year, according to SEAD.