SMB and HBA's


Active Member
Jan 20, 2017
Would someone be kind enough to give me a quick education on SMB and HBA's?

Several Supermicro and Intel HBA's and/or backplanes that I own include a small 4 pin connector labelled PEM_SMB (Intel) or JVNI2C (Supermicro). Up until I examined the Intel card a little closer today, I had always assumed these were some sort of proprietary connection used to help the motherboard identify/address the PCIe devices connected downstream of the cards.

This morning I noticed that there are two sets of empty 3 pin jumpers on the Intel card labelled "Retimer_SMB" and "BMC_SMB". I'm curious if these jumpers might be used to specify how the card identifies itself to the motherboard (e.g. if, rather than use the 4 pin connector "PEM_SMB", one might be able to activate one of the jumpers for RETIMER_SMB or BMC_SMB and instead have the card talk to the system directly through the PCIe slot).

The factory configuration of my SM NVMe server uses a RSC-U2N4-6 riser card which includes, but does not use, the JVNI2C port... This adds to my confusion as, up until now, I've never been able to get a PCIe card that has the JVNI2C port to function on a board which does not include it. I suppose there are two possibilities:

-The JVNI2C port on the RSC-U2N4-6 riser card is meant to be plugged in to an HBA installed in its x16 slot
-The JVNI2C port on the riser card is meant to be plugged in to a motherboard, but in this application the riser card is able to identify itself without it.

Any and all feedback is much appreciated!!