Mini-SAS Connector Puzzle: Understanding the Connections

connectorsas

Can anyone clearly define the difference between the Mini-SAS HD SFF-8644 and SFF-8614 connectors please?
The SFF-8644 seems to be the more widely recognised 'male' connector but SFF-8614 seems also to be in use. I cannot find if there is any discernible difference between the two but I don't want to order cables with the wrong type of connector.
The one possibility I have come across is that the 8614 is the 4-lane version and the 8644 is the 8-lane version although it does specify "8-lane with dual connector" which muddies the water somewhat. I would appreciate confirmation of this if anyone knows for sure as this is from Wikipedia (Serial-Attached SCSI).
Thanks

Best Answer

An interesting question which I thought I would have a go at answering.

Seagate provide a list of the SFF specifications but all of the links direct you to the current host, the Storage Networking Industry Association (SNIA). Here we can search for each specification which yields the following.

If we take a look inside SFF-8614 there is the following note:

Update History:

The content of this specification was formerly contained in SFF-8644, and it was broken out into a separate specification so that it could be referenced by higher speed variations.

Reading the two specifications my interpretation follows.

The content which was moved to SFF-8614 discusses the physical form of the connectors; both the "fixed" part (socket) and the "free" part (plug). There's even a heat sink specification for a socket (!).

The content of SFF-8644 which remains is almost nothing. The only purpose I can see to this document now is a link between the physical form (which the document refers to as the "Connector Mechanical") with the SAS-3 PCIe 3.0 Application Interface (what I tend to think of as the electrical specification, or signal specification).

I haven't had time to digest the details but SFF-8644 contains an illustration taken from SFF-8614 and it looks like an SFF-8644 connector may be x4 or x8 and I would assume the cable assembly should specify which (although perhaps x4 is 'normal enough' to go unspecified, with x8 being explicitly stated). I've uploaded a copy of Figure 4-1 General View of Configurations below from SFF-8644 to illustrate.

The SFF-8614 spec also states:

2.1 Industry Documents

The following interface standards and specifications are relevant to this Specification.

  • INCITS 519 SAS-3 (Serial Attached SCSI 3)
  • INCITS 534 SAS-4 (Serial Attached SCSI 4)
  • SFF-8410 High Speed Serial Testing for Copper Links
  • SFF-8643 Mini Multilane 4/8X 12 Gb/s Unshielded Connector (HD12un)
  • SFF-8644 Mini Multilane 4/8X 12 Gb/s Shielded Connector (HD12sh)
  • SFF-8673 Mini Multilane 4/8X 24 Gb/s Unshielded Connector (HD24un)
  • SFF-8674 Mini Multilane 4/8X 24 Gb/s Shielded Connector (HD24sh)

This makes it slightly more clear that you probably want to buy SFF-864{3,4} or SFF-867{3,4} cables, rather than SFF-861{3,4}. With the 3 variants being un-shielded (presumably internal) and 4 variants being shielded (presumably external).

I hope this helps your understanding. It has certainly helped mine!

SFF-8614, FIGURE 4-1 GENERAL VIEW OF CONFIGURATIONS

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