The Incompatibilities between M.2 and Samsung NGSFF/NF1

Incompatibilities between M.2 and Samsung NGSFF/NF1

As the standards committee behind PCI Express and the related standards, PCI-SIG issued a warning which is about the incompatibilities between M.2 and Samsung’s NGSFF/NF1 SSD form factor.

Indeed, this warning did not directly indicate that it is Samsung by name. But, it indirectly indicated it was based a new form factor on a mechanically identical M.2 connector but didn’t introduced a new keying option which can be used to prevent improper insertion of M.2 drives into NGSFF slots or vice versa.

About Samsung NGSFF/NF1

Samsung’s NGSFF was firstly introduced in 2017. It was treated as a proposed replacement for M.2 and U.2 SSDs in the datacenter applications.

These goals are quite similar to the competing EDSFF standards from the Intel’s Ruler: the supplied power exceeds M.2’s 3.3V supply, allow cards hot-swapping, and more. Actually, Samsung’s standard re-uses almost all of M.2’s data and ground pin assignments, but it removes the 3.V supply and adds 12V power elsewhere.

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Then, at first, Samsung wanted to name its standard as M.3, but for some reasons, the name was changed to NGSFF before going public.

Although Samsung has pursued the standardization via JEDEC with a new name of NF1 for the form factor, it did not have some development. However, Samsung doesn’t give up. It still moves forward with the deployment of NGSFF SSDs, and owns some partners including OEMs like Supermicro and AIC.

PCI-SIG’s Complaints

The complaints about NGSFF are about the conflict pin assignments for the M.2 M-keyed connector.

Samsung needed to add 12V power and PCIe dual-port capability, thus, it made use of some previously-unassigned pins which the existing M.2 drives and sockets leave disconnected.

As a result, some of Samsung’s new pin assignments are incompatibility with new assignments for the forthcoming M.2 revision 1.2 specification. Here, some of the conflicts have a risk even with currently existing products.

For instance, the NGSFF SSD has a ground connection on pin 20 which is adjacent to pin 18 where the M.2 sockets can provide 3.3V power. Thus, when an NGSFF SSD is inserted into a standard M.2 socket, it may cause a short circuit.

Except the above mentioned pin, there are also five other pins which NGSFF applies which are in unassigned state in revision 1.2 of the M.2 specification. It is obviously, more conflicts will appear in the future.

The Current Situation

The conflicts are existed. Moreover, some degree of electrical compatibility between NGSFF and M.2 version 1.1 is still possible, which proves that Samsung’s re-use of the same mechanical connector with a similar pin-out has some utility.

The Taiwanese makers, Minerva, can make almost all kinds of storage adapter, and it has many adapters which provide slots for M.2 and NGSFF SSDs.

More importantly, the analysis about these conflicts is more theoretical. In the real world, the risk may not happen for hot-swappable drives mounted to trays do not accept M.2 SSDs, and the adapter can kill the risk of damage.