An old Biostar motherboard I am using for my Mythtv backend has two SATA connectors, but they are only compatible with the 1.0 spec. OK, so the drive should recognize that and revert to SATA I compatibility mode. No, at least not Western digital drives. My motherboard refused to recognize the drive.
I remembered from an old Tech Guy podcast that someone was complaining that his motherboard wouldn’t acknowledge the drive without the 150MB/s pins jumpered. Remembering that I searched and found this document from Western digital explaining what the jumper pins were on their SATA drives — of course OEM drives come with no such documentation, remember when WD actually used to put the jumper settings on the drive itself?
So jumping pins 5 and 6 enables 150MB/s transfer speeds. After reconnecting the drive: Viola! The motherboard enumerated the SATA drive and I was on my way.