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Phase-change memory samples

Feb 11, 2008 — by Jonathan Angel — from the LinuxDevices Archive — 4 views

Intel and STMicroelectronics have begun sampling phase-change memory (PCM), a potential flash memory replacement that uses heat instead of electrons to store data. Code-named “Alverstone” in this 128Mbit, 90-nanometer implementation, it outdoes flash by providing bit alterability, faster speed, and lower power consumption, the… companies say.

(Click here for a larger view of Alverstone)

The two companies have been working on PCM since 2003. The technology uses chalcogenide glass, which contains elements such as sulphur, selenium, or tellurium. This material, which has also been used on rewritable optical media, can exist in both crystalline and amorphous states. Heat is used to toggle between them, thereby storing a single bit of information.

In a paper delivered this week at the International Solid States Circuits Conference (ISSCC) in San Francisco, Intel and STMicroelectronics said they have found a way to get the chalcogenide material into two additional states, semi-crystalline and semi-amorphous. This multi-level cell (MLC) technology effectively doubles storage capacity, according to the companies.

Flash memory is far from “broken”; in fact, Intel and Micron recently announced high-speed NAND flash technology they say will be five times faster than current products. However, flash stores data by modulating electrons stored within the gate of a transistor, requiring relatively large voltages and amounts of time. PCM will offer substantially lower power consumption, and speed approaching that of DRAM, the companies hope.

Another cited advantage of PCM is bit alterability, meaning that a single bit can be changed at any time. With flash, changing one bit can require erasing a “block” of data that may contain hundreds or even thousands of bits. This slows down writes and increases wear.


Intel and STMicroelectronics did not provide a timetable for introduction of PCM, but hinted at its eventual market by saying the Alverstone part “is intended to allow … cellular and embedded customers to learn more about PCM and how it can be incorporated into their future system designs.”

Alverstone and future PCM products will become part of Numonyx, a new independent semiconductor company created by STMicroelectronics, Intel, and investment company Francisco Partners. Until PCM is ready for sale, Numonyx will concentrate on selling traditional memory products.

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