This may help:
The SATA standard also specifies a
power connector sharply differing from the four-pin
Molex connector used by PATA drives and many other computer components. Like the data cable, it is wafer-based, but its wider 15-pin shape should prevent confusion between the two. The power connector is known to be quite flimsy, as the thin plastic tops of the connectors (see power connector picture at right) will often break off when even the slightest force is used to wiggle it whilst it is plugged in (as is often required in tight spaces), rendering the connector useless. The seemingly large number of pins are used to supply three different
voltages if necessary — 3.3
V, 5 V, and 12 V. Each voltage is supplied by three pins ganged together, of remaining pins 5 are for ground. The last pin, pin 11, is used in newer drives for "staggered spinup" . The supply pins are ganged together because the small pins by themselves cannot supply sufficient current for some devices. One pin from each of the three voltages is also used for
hotplugging. The same physical connections are used on 3.5-in (90 mm) and 2.5-in (70 mm) (notebook) hard disks. Some SATA drives include a PATA-style 4-pin Molex connector for use with power supplies that lack the SATA power connector.
**Adaptors are available to convert a 4-pin Molex connector to SATA power connector. However, because the 4-pin Molex connectors do not provide 3.3 V power, these adapters provide only 5 V and 12 V power and leave the 3.3 V lines disconnected. This precludes the use of such adapters with drives that require 3.3 V power. Understanding this, drive manufacturers have largely left the 3.3 V power lines unused. **