My Supermicro motherboard has a "vertical S-SATA connector". The manual simply says "A vertical S-SATA connector, offers four S-SATA 3.0 connections (S-SATA 0-3)". I took a picture of it and it looks like it has 18 pins. I've had no luck finding any kind of 18-pin SATA cable. What kind of connector is this?
Taken from there
SFF-8087 Internal four channel connector (data only)
The SFF-8087 connector is a very widely used connector type that is commonly used today on SAS cards. It carries the equivalent of four SATA/ SAS 7-pin connections through a SFF-8087 to SFF-8087 cable providing 12gbps of throughput using SAS or SATA II 3.0gbps devices.
In fact, many makes of SFF-8087 cables look like four 7-pin cables were sheathed together and terminated at each end by SFF-8087 endpoints. SFF-8087 connectors tend to have locking mechanisms that snap into place when a cable is inserted. This generally keep the connections secure over time even if there is minor chassis movement and vibration.
When purchasing SFF-8087 cables, pay close attention to both ends of the cables. There are many variants which commonly include SFF-8087 to SFF-8087, SFF-8087 to SATA breakout/ four 7-pin connectors, and SFF-8087 to SFF-8088. One needs to ensure they are purchasing the correct cable for their application.