What is 3D XPoint?

3D XPoint is a cutting-edge memory storage technology co-developed by Intel and Micron Technology. This innovative solution aimed to bridge the gap between traditional dynamic RAM (DRAM) and NAND flash memory, effectively creating a new category known as storage-class memory. This type of memory provides a middle ground, offering features that appeal to both high-speed, low-latency applications and long-term data storage.

The flagship product of this joint endeavor was Optane, which utilized the 3D XPoint technology. However, the partnership faced challenges, especially regarding cost and profitability expectations. In 2021, Micron exited the collaboration, selling its fabrication plant to Texas Instruments. By 2022, Intel halted the manufacturing of Optane memory components and stopped supporting it on newer generations of central processing units (CPUs).

How 3D XPoint Memory Works

Upon its introduction in 2015, Intel and Micron proclaimed that 3D XPoint would be up to 1,000 times faster and have significantly greater endurance than NAND flash. Additionally, they claimed it would boast ten times the storage density of conventional memory. Although early products demonstrated impressive speed and endurance, they ultimately did not consistently meet the lofty expectations set forth by their developers.

The operational architecture of 3D XPoint is notably different from other flash products, as it is based on phase-change memory technology. This memory design, which dates back to the 1970s, employs a unique, transistorless cross-point architecture. In this setup, selectors and memory cells are positioned at the intersections of perpendicular wires. By sending a current through both the top and bottom wires that intersect at a cell, individual cells can be accessed.

To maximize storage density, 3D XPoint cells are stacked to form a three-dimensional structure. Each cell holds individual data points, representing either a ‘1’ or a ‘0’ through changes in the material’s bulk properties. This change alters the cell’s resistance, with high and low-resistance states correlating to digital data. Importantly, these cells retain their values even without power, making them a form of non-volatile storage.

For read and write processes, a specific voltage is applied to the surrounding wires. Write operations involve triggering the selector and transmitting voltage to the cell to affect its resistance. Conversely, read operations use a different voltage to determine the state of the cell’s resistance. This granular bit-level writing capability enables 3D XPoint to outperform NAND flash, where entire blocks must be erased before new data can be written.

Major 3D XPoint Products

Intel began shipping its initial 3D XPoint products in early 2017, with Optane memory targeted at consumer PCs following suit. These cache driving solutions initially came in capacities of 16 GB and 32 GB and were designed to work with Intel’s seventh-generation Core processors, connecting via M.2 slots on Intel 200 series motherboards. However, support for Optane was discontinued with Intel’s 12th and 13th-generation CPUs, marking the end of an era for these products.

The Intel Optane memory line features various offerings, including:

• Intel Optane Memory Series
• Intel Optane Memory M10 Series
• Intel Optane Memory H10 with Solid State Storage
• Intel Optane Memory H20 with Solid State Storage

3D XPoint Speed and Performance

One of the most revolutionary aspects of 3D XPoint architecture is the elimination of the traditional 4 KB block storage format used in NAND, facilitating quicker data read/write processes. Although this technology offered a significant performance advantage, it didn’t consistently meet the high expectations set by Intel and Micron.

While not as fast as DRAM, 3D XPoint does provide non-volatile memory, which distinguishes it from traditional storage options. Price-wise and performance-wise, it sits comfortably between DRAM and NAND flash memory. Intel claimed that their 375 GB P4800X drive could perform five to eight times faster than their NAND flash-based DC P3700 model, achieving an impressive 500,000 IOPS at low queue depths.

Industry experts speculated that limitations in the PCI Express (PCIe) bus and necessary system modifications hindered 3D XPoint from achieving its full potential. Innovations such as using a compiler for persistent memory and rewriting applications to leverage the technology could further enhance performance.

3D XPoint Product Costs

Despite the discontinuation of new production, Intel Optane memory cards remain available in various models, with pricing examples as follows:

• Optane solid-state drive (SSD) P1600X Series 118 GB: $71
• Optane Memory M10 16 GB: $15
• Optane Memory H20 32 GB plus SSD storage 512 GB: $80
• Optane Memory H10 32 GB plus SSD storage 512 GB: $116

3D XPoint Use Cases

3D XPoint was designed to serve as an intermediary storage layer between NAND flash and DRAM. This structure allows for a tiered storage approach, where high-intensity data and applications, requiring fast access, are stored on the flash level, while less frequently accessed data is moved to cheaper storage solutions. 3D XPoint provides an additional layer of performance for applications demanding rapid processing.

Moreover, beyond high-speed storage and caching, 3D XPoint technology also facilitates memory extension and replacement. It aims to enhance server memory exponentially while reducing DRAM requirements for specific workloads. Intel outlined three methods for memory enhancement using 3D XPoint Optane SSDs:

1. Employing operating system paging mechanisms to store data on PCIe-attached SSDs when DRAM reaches capacity.
2. Utilizing optimized applications.
3. Implementing Intel’s Memory Drive Technology available on its Xeon processors.

For use cases that require additional memory, Intel also anticipated the release of dual in-line memory modules (DIMMs) with 3D XPoint technology. Suggested applications leveraging 3D XPoint Optane include:

• Expanding virtual DRAM sizes
• Enabling larger databases
• Mitigating big data network bottlenecks
• Enhancing high-performance computing applications
• Improving instance storage performance in cloud environments
• Meeting the storage needs of hybrid cloud infrastructures
• Serving as primary memory tiers in hyperconverged systems

3D XPoint vs. Compute Express Link

Compute Express Link (CXL) technology, developed by the CXL Consortium, serves as an open industry standard interface designed for high-speed communication between CPUs and memory components. It not only manages memory coherence but also supports resource sharing among different memory types, making it crucial for applications in artificial intelligence and machine learning.

CXL operates atop PCIe architecture, facilitating the addition of memory (like DRAM blocks). In comparison, Optane stands as persistent memory that provides low-latency benefits distinct from those found in NAND flash storage.

With the latest CXL specification 3.1 announced in November 2023, this technology evolves, maintaining backward compatibility while building on the momentum of its predecessors.

The Future of 3D XPoint

The trajectory of both Intel and Micron has shifted toward the CXL standard, moving away from 3D XPoint. While Optane-based products are still available, they are no longer being manufactured and lack support in newer CPU generations from Intel.

The evolution toward CXL signifies a new era in memory technology, one with vast implications for future data center and AI applications.