Going beyond DRAM and Flash Memory

Phase-change memory (PCM). In this photo, the experimental multi-bit PCM chip used by IBM scientists is connected to a standard integrated circuit board. The chip consists of a 2 × 2 Mcell array with a 4- bank interleaved architecture. The memory array size is 2 × 1000 μm × 800 μm. The PCM cells are based on doped-chalcogenide alloy and were integrated into the prototype chip, serving as a characterization vehicle in 90 nm CMOS baseline technology. Credit: IBM Research

The quest towards ever more dense, fast and cheap memory storage continues, even though Moore's law has come to an end. This is pursued with new technology, rather than through the shrinking of transistor size in existing ones.

One such technology is PCM, Phase-Change memory, where the material used can assume crystalline, amorphous and multi-crystalline structure. Each of these structures can be associated with a value, hence it can store data.

PCM is not new, it is based on the properties of chalcogenide glass whose initial studies go back to the 1960ies. The interest in this type of Non volatile memory (NVM), a memory that retains the data when the power causing the storage of the data has been removed, has been revamped by the difficulties in furthering DRAM and Flash memory.

At IBM a team of researchers have demonstrated the possibility to store, in a reliable way, 3 bits per PCM cell. This adds to the existing PCM technology what was missing: the low cost, since by storing 3 bits per cell one is basically dividing the cost of the chip by 3.

Take a look at the clip to get an overview of the technology and read the article to get the details.

It is interesting to see that by exploring new technologies and coming up with new architectures we can keep improving the chips, beyond Moore's.  This is the path pursued by the IEEE Group Rebooting Computing.

Author - Roberto Saracco

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