Quote:
The cable that Western Digital included with the drive was a unified plug that covered both the power and data connectors together. So I guess I assumed that it was supposed to be getting power from the motherboard somehow, and that the "legacy" power connector wasn't intended to be used except as a backup if you didn't have the right cable or something.

Actually, that cable is included to blank out the power connector, to ensure you don't connect both the SATA power and molex power. Simply a mistake prevention device, and not something to power the drive through the bus.