See section 8.2.11 of the attached document. Detection of 80W cable is done both by the host (looking for a grounded pin 34), and by the attached drives. The host queries the drives for what they saw after reset.

Basically, Pin 34 in the Host Connector shall not be attached to any cable conductor, and shall be attached to Ground within the connector. This signal is called PDIAG, or CBLID.

The conductor for PDIAG (conductor 66, 67, or 68 .. see Table 15/16 in the document) should not itself be grounded -- the drives use it to detect/communicate the cable type among themselves.

Oh -- if just hooking up a single drive (rather than a pair on the cable), ensure it is using the MASTER connector (end of cable), not the SLAVE connector (middle of cable). They're different.

And jumper the drive(s) (SATA converters) to use CSEL (cable select), rather than hard-jumpering them as master or slave.

Cheers