What is SATA Express (Serial ATA Express) ?

The standard interface makes easy compatibility and installation between PC and storage devices possible.

On the host side, the SATA Express connector can be backward compatible with the standard Serial ATA data connector. At the same time, two PCI Express channels are also available as pure PCI Express connections to the storage devices. A separate signal from the drive tells the host whether it is SATA or PCIe.

Features

• Supporting both SATA and PCI Express storage devices, the SATA Express interface exposes two SATA 3.0 (6 Gbit/s) ports and two PCI Express 2.0 or 3.0 channels (but not simultaneously) through the same host-side Serial ATA Express connector.
• A pure PCI Express connection is provided by Exposed PCI Express lanes between the host and the storage devices. And there is no additional bus abstraction layer.
• PCI Express’s choice uses many channels and different versions of PCI Express to extends the performance of the SATA Express interface. To be more specific, the overall bandwidth of 1000 MB/s can be provided by using two PCI Express 2.0 lanes, while 1969 MB/s can be provided by using two PCI Express 3.0 lanes. By contrast, the original bandwidth of 6 Gbit/s at SATA 3.0 is equivalent to 600 MB/s.
• There are three choices for the logical device interface and command set: Legacy SATA, PCI Express using AHCI, and PCI Express using NVMe. They are used for interfacing with storage devices connected to a Serial ATA Express controller.

Connectors

The SATA Express connectors make sure that it is possible to backward compatible with legacy SATA devices without additional converters or adapters.

Five types of connectors are available: Host plug, Device plug, Host receptacle, Host cable receptacle, and Device cable receptacle. They differ in position and purpose.

Host plug

On add-on controllers and motherboards, the host plug accepts traditional standard SATA data cables to be backward compatible. So it provides connectivity for at most two SATA devices.

Device plug

Used on SATA Express devices, device plug allows the SATA Express device to be plugged into MultiLink SAS socket or the U.2 backplane to be partially backward compatible. But if connected in that way, the SATA Express device will only work correctly when the host supports the PCI Express device.

Host receptacle

On backplanes, the host receptacle accepts a SATA device to be backward compatible. It mates with the SATA Express device directly, which makes for cableless connections.

Host cable receptacle

Used on SATA Express cables, host cable receptacle is the host-side connector, with no backward compatibility.

Device cable receptacle

Used on SATA Express cables, the device cable receptacle is a device-side connector. And it accepts one SATA device to be backward compatible.

Compatibility

• It fully supports the traditional SATA 3.0 storage. Besides, it ensures the SATA Express’s device-level backward compatibility, including required operating system support and electrical level.
• Mechanically, the host-side connector maintains its backward compatibility in a USB-like manner.
• The host-side SATA Express connector has backward compatibility. So it is possible to connect legacy SATA devices to a host that is equipped with a SATA Express controller.

Sum-It Up!

In short, this page fully introduces the SATA Express (Serial ATA Express). It aims to give readers a general understanding of its features, connectors, as well as its compatibility.