What's the additional 8 pin connector on the 4x 7-Pin SATA adapter for?

Hardware
1

Hello,

Slight noob question (still trying to figure out all these server connectors).

When purchasing my bare bones HL15 I selected the SFF 8673 -> 4x 7-Pin SATA adapters. I was getting everything ready to put into the motherboard and noticed the SATA side of the connector has this extra 8 pin connector labeled P4. What is this used for?

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When googling SFF-8643 to 4x sata adapters most of them don’t have this extra 8 pin connector.

2

Second image showing the front of the connector

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3

After some further research it looks like it’s a “Sideband connector” or a “SGPIO” connector used to for monitoring the backplane and the drives

4

Yeah, looks like a sideband connector but I’ve never even heard of them before researching for this HL15.