▷ Sata express: what it is and why it is not currently used

Storage technology has evolved in recent years a lot with the arrival of SSD drives. The SATA Express connector was one of the tests that answered the need to get the most out of these storage-based drives on solid memory chips. But, how is this technology today? This and more we will discuss today in this article about this connection interface.

Index of contents

The invention of the SATA interface was without doubt one of the most important steps taken in storage technologies. These had been stuck for long years in the heavy IDE interfaces with those cables worthy of a trampoline. Then came the SSD drives with which the SATA interface also fell short, and that is when SATA Express appeared, although for a short time as we see below mainly due to its competitor the M.2 connector.

What is the SATA Express connector

SATA Express is a high-speed connection interface based on SATA (Serial ATA) technology that supports devices of this type and also PCI Exress (PCIe). This interface is also commonly known as SATAe, which at no time should we confuse with the eSATA (External SATA) connector intended for External SATA drives.

SATA Express was implemented as the SATA 3.2 specification in 2014 to provide it with the capacity to support PCIe devices. While SATA 3.0 was, and is capable of, a data transmission rate of up to 6 Gb / s (600 MB / s), the SATA Express interface is capable of 16 Gb / s or whatever it is. the same, 1.97 GB / S.

With this initiative, the SATA designers group decided that doubling the speed of its basic interface was too costly and implied a higher consumption of electricity. For this reason, they decided to turn the technology over and adapt their data transmission protocol to a new interface based on PCI-Express. In this way they achieved higher speeds with the own consumption of a PCIe connection.

In this way, SATA Express, in addition to working with the classic AHCI (Advanced Host Controller Interface) communication protocol, can also work with the NVMe logical interface, in this way it is able to take full advantage of PCIe storage units and also provide compatibility. In older teams with AHCI for this type of units.

Technical characteristics of SATA Express

As we have already seen, the most important property of SATA Express is that it is capable of supporting both PCI Express (in NVMe logical interface) and SATA (in legacy AHCI interface), thanks to the connection via PCI Express 2.0 or 3.0 buses or by two SATA 3.0 ports connected at once along with another small power connector

The devices that we connect through the first option, that is, through PCIe, will obtain a direct connection between the motherboard and the storage unit, since no extra layer will be necessary to make both connection protocols compatible. This is mainly the most significant advantage of SATA Express

But not everything is gold, and it is that this interface has a problem that has been the reason why it is so little used today. Although SATA Express is initially capable of supporting both protocols for storage devices, only both can be connected simultaneously. This implies that when we connect a SATA hard drive to our computer, the computer will work only with the one that has been connected, and if we connect a PCIe drive it will only work with this one, but at no time with both simultaneously.

SATA Express Physical and Logical Connection Configuration

SATA Express has three different options to communicate with the storage devices connected to it:

SATA Legacy

This protocol uses the compatibility with the legacy SATA devices, so they will be connected through the SATA's own AHCI controller and with two SATA 3.0 ports and the small extra connector.

PCI Express with the use of AHCI

In this second case, the device will be connected to the PCIe bus but the communication protocol will be AHCI again, so we will obtain speeds much lower than what a normal PCI Express connection can be and we would not be taking advantage of the true power of a PCI Express storage unit.

PCI Express using NVMe

This is the most optimal option, since it takes advantage of all the speed of the PCIe units connected to the interface itself thanks to the NVMe communication protocol. It is in this way that we will obtain the maximum data transmission capacity of the unit and the port.

SATA Express connectors

Due to the compatibility between SATA and NVMe we will have several types of SATA Express connectors available:

• PCI Express connector: This port will be similar to the one we have available in our base bale as PCIe. It has two buses that we can differentiate due to their different size. This bus also has a compatible version on old motherboards to work with PCIe SSDs

• Connector made up of two SATA 3.0 and extra connector: This interface is made up of two typical SATA 3.0 ports and a small extra power supply connector to form three buses in total.

The positive aspect of this last connector, is that it provides the capacity of backward compatibility with PCIe units. That is, we can use two normal SATA cables to connect them to the SATAe SSD in addition to a power connector that this unit needs for operation. It will be in this case, the small connector that we have discussed in addition to the two SATA 3

Why SATA Express is not currently used

The truth is that despite everything we have said and the greater speed that we obtain thanks to this connector, it is currently little used. The fundamental reason for this is because there is another interface between us that is destined to end SATA at some point. This is the M.2 interface.

M.2 also emerged practically simultaneously with SATAe but it does not have the limitations we have discussed about the simultaneous use of SATA and PCIe and speed limitations. And it is for this reason that manufacturers have opted to create M.2 drives that also use the NVMe protocol and not SATAe.

In addition, we must recognize that the SATA Express bus is quite large and it is as if we return to the time of those enormous IDE cables of a thousand and one cables

With this we conclude our technical and educational review of SATA Express.

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Do you have a SATA Express drive? Leave us in the comments what you think about this interface and if you prefer M.2.