What is Phase Change Memory?

Phase Change Memory is type of non-volatile computer memory (NVRAM) that is sometimes referred to as “perfect RAM” due to its superior performance characteristics. Phase Change Memory is also referred to as PCM and PCRAM by different groups.

Regardless of the acronym used, Phase Change Memory represents an innovative type of memory technology with great potential storage application use cases. Phase Change Memory offers the promise of fast RAM speeds, but can be used to store data with low power requirements.

Phase Change Memory is a technology that has been in various stages of research and development since the late 1960’s, though mainstream commercial implementation in storage has been limited. However, as you’ll see below, many vendors are investing in the technology, and it likely has a bright future.

Phase Change Memory Definition

Phase Change Memory offers a key advantage of NVRAM: unlike Dynamic Random-Access Memory (DRAM) which is another common type of system memory, NVRAM allows information to be retained when the system is powered off.

Phase change memory uses a special alloys, including Germanium Antimony Tellurium (GST), which have innovative characteristics that enable the non-volatile storage. The alloy can be altered with heat to have two different states or “phases” (crystalline and amorphous) which is how data is stored.

An experimental Phase Change Memory chip used by IBM scientists (Credit: IBM Research)

Benefits of Phase Change Memory vs. Flash

There are multiple benefits that are associated with Phase Change Memory in comparison with other types of memory storage, including NAND Flash Memory

• Faster Write Cycles. PCM offers the promise of write cycles that could be significantly faster than NAND flash. NAND Flash requires data to be erased before new data is written, while PCM has no such requirement, making it considerably faster.

• Faster Access Time. Research has found that access times below 5 µs can be achieved with PCM.

• Endurance. Given that PCM doesn’t need to erase data first, vendors and researchers have estimated that Phase Change Memory can handle more write cycles than NAND flash.

• Lower Power Consumption. PCM offers the promise of lower power requirements than its NAND counterparts.

• PCM Is Executable. A unique characteristic of Phase Change Memory is that it will be able to both execute code, much like existing DRAM, as well as have the ability to store data like NAND.

Companies Developing Phase Change Memory

As noted above, Phase Change Memory is a technology that is seeing major investment by major vendors. At this point, multiple vendors have been publicly talking about their PCM efforts and technology with varying degrees of success.

IBM

• IBM has demonstrated PCM storage innovations working on its OpenPower server architecture.

• Among IBM’s research innovations is a three bit per cell PCM chip, which could provide more stability and storage than prior research which demonstrated 1 bit per cell options.

Intel

• Intel has been working on PCM since at least 2006 when it debuted the technology at its’ developer conference.

• Some elements of PCM may be part of the company’s 3D XPoint technology, though Intel does not currently specifically market a dedicated PCM solution.

Micron

• Micron had been among the leading vendors developing PCM technology, thanks in part to its 2010 acquisition of PCM pioneer Numonyx.

• After multiple fits and starts, Micron announced that it was exiting the PCM market in 2014.

Samsung

• Samsung has been working on various iterations of PCM technology for over a decade.

• The primary use case that the company is currently focused on is for embedded use within cellular phones, though there is the future potential for commercial storage devices as well.

STMicroelectronics

• STMicrolectonics holds one of the core patents that enables PCM storage.

• The company has been developing embedded PCM (ePCM) technology for automotive use cases.

Western Digital

• Western Digital’s HGST (Hitachi Global Storage Technologies) business unit has been developing a technology called DC Express to help fully enable PCM storage for a future generation of motherboards.