Date: Monday , November 02, 2015
Earlier this year, we gave an overview of the then-current state of the enthusiast SSD market, as well as some predictions on where things appeared to be headed. The last 7 months have seen no shortage of exciting announcements, and the enthusiast market has rapidly evolved in both positive and confusing ways. Let’s get up to speed on U.2, NVMe, 3D XPoint, M&A, and the rest of the alphabet and buzzword soup that make up this market.
A Note on Terminology
There has been a lot of new terminology in the SSD world, and it can get easily muddled. In the interest of clarity and consistency, we’ll use the following conventions when referring to categories of technology:
Form Factor: the physical footprint/size and shape of a drive (e.g., add-in card, M.2 stick, or 2.5" drive)
Interface: the bus used to connect an SSD to a host (e.g., SATA or PCI Express)
Protocol: the communication standard used to communicate across an interface (e.g., NVMe or AHCI)
Connector: the physical connector of a drive to a cable or socket (e.g., standard SATA connector, the PCIe 3.0 x4 edge connector, U.2/SFF-8639, M.2 connector keys)
When Intel launched the SSD 750 back in April, they chose to offer it in the traditional PCIe add-in-card form factor as well as a 2.5" drive with a then-uncommon SFF-8639 connector. The SFF-8639 connector provided a standard to carry 4 PCIe 3.0 lanes over a cable; the almost completely stillborn SATA Express standard only offered 2 lanes on a cabled interface. This was a shrewd move on Intel’s part. The SSD 750 is a serious drive with serious componentry that cannot physically be shoehorned into any of the M.2 standard form factors, and also had power requirements beyond what M.2 could deliver. Moving to the SFF-8639 approach allowed Intel to preserve the high-end small form factor market as far more people are buying than building PCs, and many of those buying PCs want something compact and well-integrated, this solution ticked all the right boxes.
Since "SFF-8639" is a mouthful, the standard has been renamed "U.2," and other drives supporting it are beginning to trickle out. Manufacturers are offering M.2 to U.2 adapters (the drives receive power through a separate cable), with the ASUS U.2 Hyper Kit shown above. U.2 is positioned to become the standard interface for NVMe drives connected over a cable.