Definition: 3D XPoint

(3D Cross Point) An earlier non-volatile memory and storage technology from Intel. Using phase change technology, 3D XPoint was available from 2017 to 2022. Less expensive and denser than dynamic RAM (DRAM), 3D XPoint was more costly than solid state drives (SSDs), although considerably faster while using less power.

Micron manufactured the 3D XPoint chips for Intel under the Optane brand, as well as for itself under the QuantX moniker.

Both Memory and Storage
Like all memory chips, XPoint was byte addressable and could thus be used like main memory or a secondary RAM bank. Because it was non-volatile, it could be used as a fast SSD or as a cache to an SSD. See cache, byte addressable and SDRAM.

Cross Point Structure

Voltage applied to the top and bottom wire of the selector causes the cell to be read or written, and transistors are not required at each cell like they are with DRAM. Unlike flash memory that has a limited life span, XPoint is not affected by the number of write cycles. (Image courtesy of Intel.)

         Byte        Non-
      Addressable  Volatile   Speed

 SRAM     Yes        No      Fastest

 DRAM     Yes        No      Faster

 XPoint   Yes        Yes     Fast

 NAND     No         Yes     Slower