Alternative memory standards have been kicking around for decades as researchers have struggled to find the hypothetical holy grail — a non-volatile, low-latency, low-cost product that could scale from hard drives to conventional RAM. NAND flash has become the high-speed, non-volatile darling of the storage industry, but if you follow the evolution of the standard, you’ll know that NAND is far from perfect. The total number of read/write cycles and data duration if the drive isn’t kept powered are both significant problems as process shrinks continue scaling downward.
Thus far, this holy grail remains elusive, but a practical MRAM (Magnetoresistive Random Access Memory) solution took a step towards fruition this week. Everspin has announced that it’s shipping the first 64Mb ST-MRAM in a DDR3-compatible module. These modules transfer data at DDR3-1600 clock rates, but access latencies are much lower than flash RAM, promising an overall 500x performance increase over conventional NAND.
Everspin’s technology uses a single magnetic tunnel junction (MTJ) and one transistor. When current is applied, spin-polari ed electrons tunnel through the dielectric barrier. Doing so means that the angular momentum of the electrons is transferred to the magnetic layer, “flipping” the polari ation. The state of the cell is “read” by measuring its resistance.
Spin-torque technology uses much less power for writes than conventional MRAM and is expected to scale to smaller geometries more effectively. The primary power advantage of MRAM is that, once “written,” cells don’t need to be refreshed. MRAM retains its data if the power is turned off, and it doesn’t draw power to retain data during active system operation.
The benefits of this type of memory are potentially enormous. The reduced power consumption MRAM offers could be used to extend battery life in mobile devices while simultaneously driving density upwards in HPC and supercomputing nodes. With that said, ST-MRAM is still years away from practical consumer applications. Everspin’s new 64Mb “DIMMs” are impressive, but current 8GB consumer DDR3 DIMMs are as cheap as $30. That’s a 1000x density difference.
This doesn’t mean ST-MRAM has to hit equal density with consumer DIMMs to become useful. Once Everspin can build 8MB ICs, MRAM could begin replacing other memory technologies in devices with small amounts of memory. The technology is still years away from mass deployment, but of all the replacement memory technologies under development, it seems the most promising.
Everspin launches new non-volatile magnetic RAM that’s 500 times faster than NAND flash
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