SFF-8470 cables come in a variety of configurations. This guide aims to help users identify the various latch types and keying configurations, and the inter-compatibility of each type.
External SAS & SFF-8470
The SFF-8470 connector is an external Serial Attached SCSI (SAS) connector, but the connection itself was adopted by SAS, from the earlier Infiniband specification. There are many vendors that offer SAS/SATA controllers with external SFF-8470 ports, and there are various external storage devices that expose an external SFF-8470 interface. Newer SAS devices with external SAS connectivity are using the SFF-8088 external Mini-SAS connector, which is different again to the SFF-8470 connectors set out below.
SFF-8470 attachment types
The connectors on a SFF-8470 cable are designed to be securely attached to the SFF-8470 device. The SFF-8470 specification defines a connection using thumbscrews, and another using latches, but in practice there are 3 connection types, because there are 2 variants of the latched connector - an ejector-type (pull) latch, and a squeeze-type latch.
These are the 3 attachement types:
The connectors on a SFF-8470 cable may include key-slots, which will mate with their corresponding keys on a SFF-8470 recepticle. Furthermore, the keying configurations vary by the attachment types. If the recepticle on the SFF-8470 device has keys, then the SFF-8470 connector on the cable must have the same keying and attachment type, but if the recepticle does not have keys, then the SFF-8470 connector on the cable does not require (but may still include) key-slots, however the attachment types must still match.
The keying for thumbscrew type attachments is different to the keying for latch type attachments, so a cable with a thumbscrew connector cannot be mated with a latched recepticle, and likewise, a cable with a latched connector cannot be mated with a thumbscrewed recepticle. Furthermore, an ejector-type latched connector requires a compatible recepticle, and a squeeze-type latch requires a compatible recepticle.
The drawings below depict the differences in key-slots on thumbscrew-type connectors, and latch-type connectors, but the differences in latch-type attachments is not shown. Note the key-slot differences... The thumbscrew connector has 4 slots on the upper edge, and 3 slots along the bottom, while the latched connector has 4 slots on the upper edge (in slightly different positions), and 2 slots along the bottom edge.
Connections between SFF-8470 devices
Despite the non-matability of various keyed/unkeyed and thumbscrewed/latched cables, it is possible to connect 2 SFF-8470 devices that use different keying/attachment configurations - you just need a cable that has the correct keying/attachment combination on each end of the cable. For example, you can get a cable with a keyed/thumbscrew combination on one end, and a keyed/ejector latch combination on the other.
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