According to #Micron, #3DXPoint has many technical and operational challenges, such as 100 new materials raising supply chain issues, cutting fab throughput by 15%, 3x-5x increase in capital expenses compared to planar #NAND, and heavily depending on lithography tools. Therefore, 3D XPoint becomes expensive. The 2nd generation 3D XPoint with 4-layer stacking is expected to be about 5 times more expensive than planar NAND. So, it seems difficult to be an affordable storage device. Instead, 3D NAND will serve the storage market. According to Intel/Micron, 3D XPoint is aiming at high-end SSD and DDR4 NVDIMM markets. Though, 3D XPoint-based SSD will serve niche market because of cost issue. The sweet spot of 3D XPoint should be the DDR4 NVDIMM because of low read latency (i.e. ~100ns). The configuration of DDR4 NVDIMM is shown below. Data comes to DRAM from CPU and copied to 3D XPoint. Then, the data goes back to CPU from 3D XPoint. It is possible because 3D XPoint has low read latency. However, because 3D XPoint has much less endurance compared to DRAM and its write speed is very slow, it cannot directly replace DRAM. Instead, as a shadow of DRAM, data in DRAM is copied to 3D XPoint in order to expand the size of main memory. In this case, DRAM works as a buffer for 3D XPoint. As a result, 3D XPoint will significantly replace DRAM if it works well.
http://www.eetimes.com/author.asp?section_id=36&doc_id=1330829
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