What the companies didn’t explain then – and haven’t really done since – was how 3D XPoint operates. Most observers suggested that 3D XPoint would be an update on phase change memory (PCM), a technology developed by both companies. But Intel says no. Suggesting that 3D XPoint ‘doesn’t use electrons’, it also says that it’s not based on PCM or memristor technology.
Intel planned to launch 3D XPoint based solid state drives (SSDs) under the Optane brand ‘early in 2016’. For whatever reason – likely to be manufacturing yield related – Optane SSDs have only just launched and Micron’s version – QuantX – has yet to be seen.
3D XPoint is one of the technologies vying to be a universal memory: something which is as cheap as DRAM, as fast as SRAM and non volatile like flash. The Optane SSD isn't cheap: the 375Gbyte device just announced will cost more than $1500. But it does appear to hit the spot when it comes to speed and non volatility.
Interestingly, the SSD can be configured to appear to an operating system as DRAM – in other words, a massive cache memory. A high end controller could, in theory, push data into and out of the SSD rapidly through operations like prefetching, boosting performance.
While the focus has been on 3D XPoint memory, Intel insisted that Optane would be a ‘bundle’ – alongside 3D XPoint, there is a memory controller, a PCIe interface, plus software and some other hardware elements. Could it be this combination which brings the performance boost over NAND based SSDs, rather than the memory alone? All that remains is for Intel to explain how the memory works.