3D XPoint (pronounced three-D cross point) is a non-volatile memory (NVM) technology developed jointly by Intel and Micron Technology. It was announced in July 2015 and is available on the open market under the brand name Optane (Intel) since April 2017. Bit storage is based on a change of bulk resistance, in conjunction with a stackable cross-gridded data access array. Initial prices are less than dynamic random-access memory (DRAM) but more than flash memory.
As a non-volatile memory, 3D XPoint has a number of features that distinguish it from other currently available RAM and NVRAM. Although the first generations of 3D XPoint were not especially large or fast, as of 2019 3D XPoint is used to create some of the fastest[weasel words]SSDs available, with small-write latency. As the memory is inherently fast, and byte-addressable, techniques such as read-modify-write and caching used to enhance traditional SSDs are not needed to obtain high performance. In addition, chipsets such as Cascade Lake are designed with inbuilt support for 3D XPoint, that allow it to be used as a caching or acceleration disk, and it is also fast enough to be used as non-volatile RAM (NVRAM) in a DIMM package.
Development of 3D XPoint began around 2012. Intel and Micron had developed other non-volatile phase-change memory (PCM) technologies previously;[note 1]Mark Durcan of Micron said 3D XPoint architecture differs from previous offerings of PCM, and uses chalcogenide materials for both selector and storage parts of the memory cell that are faster and more stable than traditional PCM materials like GST. But today, it is thought of as a subset of ReRAM.
3D XPoint has been stated to use electrical resistance and to be bit addressable. Similarities to the resistive random-access memory under development by Crossbar Inc. have been noted, but 3D XPoint uses different storage physics. Specifically, transistors are replaced by threshold switches as selectors in the memory cells. 3D XPoint developers indicate that it is based on changes in resistance of the bulk material. Intel CEO Brian Krzanich responded to ongoing questions on the XPoint material that the switching was based on “bulk material properties”. Intel has stated that 3D XPoint does not use a phase-change or memristor technology, although this is disputed by independent reviewers.
3D XPoint has been the most widely produced standalone memory based on other than charge storage, whereas other alternative memories, like ReRAM or MRAM, have so far only been widely developed on embedded platforms.