Future computer memory – Memristors, cheaper MRAM, and Phase change memory

Semiconductor manufacturers are developing other solid-state technologies, some of which could succeed flash and other forms of solid-state memory in the not-too-distant future.

451 Research provides computer memory analysis at computerweekly.

Chip makers have been approaching the limits to which they can reduce NAND flash manufacturing process sizes for some time.

In 2013, the time span for that forecast was effectively delayed for five or six years by Samsung’s announcement it had begun volume production of NAND flash chips featuring a 3D internal architecture.

Flash prices are now widely expected to continue to descend at about the same rate as they have been for the last few years.

This will continue until the process size for 3D NAND flash has reached about 10nm at around the end of this decade. At that point, the consensus is there will be little or no prospect of reducing NAND flash costs further.

451 Research believes eventual flash replacement will not happen until well into the next decade.

Candidates to replace flash storage

ReRAM/Memristor

Resistive RAM or ReRAM – also known as RRAM and memristor memory – stores data by flipping resistors between two stable states. Compared to NAND flash, it promises higher performance, vastly longer life and lower power consumption.

ReRAM is being developed by a number of suppliers, of which HP has the highest profile. HP describes memristor as a form of ReRAM and says it can be used to create solid-state storage that provides 10 times the performance of NAND flash, with 10 times less power consumption and longer life.

However, the ReRAM that HP envisages will not be fast enough to compete with SRAM or DRAM

Magneto-resistive RAM

Magneto-resistive random-access memory (MRAM) is already being used as an alternative to SRAM and offers similar performance levels but is more physically dense.

But MRAM is currently set to be more expensive than both DRAM and SRAM, and this means, initially at least, that its biggest appeal will be in applications where its non-volatility will compensate for its higher cost.

However, a variant of MRAM that has recently entered volume production may enable much lower costs and if that happens, MRAM could also be a rival to NAND and NOR flash, against which it offers a far longer life and greater performance.

Phase-change memory

Phase-change memory (PCM) is also known as PRAM and PCRAM. The technology has the potential to provide non-volatile storage that heavily outperforms NAND flash and offers a considerably longer write life.

IBM has described PCM as having “superb” scalability due to its ability to be produced at small process sizes with consequently higher data densities and lower costs.

The potential uses of PCM range from a replacement to NAND flash through an intermediate storage medium sitting between flash and DRAM in terms of performance and cost, to the ultimate role as a universal or “storage class” memory that would replace the entire portfolio of SRAM, DRAM, NOR flash and NAND flash.

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