IBM shows off triple-level cell phase change memory and says PCM can be used as faster adjunct to flash storage and extension to DRAM memory
IBM has achieved a breakthrough in phase change memory (PCM) that it says will bring it close to the cost of flash and allow it to be used with flash and Dram, for cache, memory and to speed database access, for example.
The breakthrough – demonstrated to the IEEE in Paris earlier in May 2016 – saw IBM show off triple level cell (TLC) PCM. This is PCM with eight resistance levels per cell, giving three 1/0 bit states in each cell.
IBM fellow Evangelos Eleftheriousaid PCM offers read times of 200 to 300 nanoseconds and 2µs to 4µs for writes. Flash storage reads are currently measured in hundreds of µs, while writes are closer to milliseconds.
Eleftheriou also said PCM can provide endurance that it 10,000 time that of flash.
Flash is also bound by having to write entire blocks of cells at a time (known as pages) and has to erase a cell before it can be written to. This is known as the program-erase cycle and is a key issue with flash. PCM, by contrast, can simply overwrite cells.
Dram, used for motherboard memory, is faster than flash, but is volatile – it doesn’t retain data when switched off, for ecample – and is too costly for bulk storage use.
PCM is made of an alloy of germanium, antimony and tellurium, which changes state when a voltage is applied to it. The key state change in PCM has been either crystalline or amorphous.
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