basically when the hard drive detects power on that pin, it stops the hard drive. Some companies went further and decided that it's pretty much safe to assume nobody will put there 3.3v on desktop computers so let's reuse those three pins in the sata power connector for other things. However, in the past there was a lot of power supplies that had no sata power connectors at all, so those molex (ide hdd connector) to sata power connectors were made, which simply ignored the 3.3v wire, the devices received only 5v and 12v.īecause these adapters are still common, a lot of devices are made to assume 3.3v may or may not be present, so they don't rely on that voltage, they just assume it's not there. In the picture above, the orange wire carries 3.3v to devices.
The SATA power connector has 3 pairs of wires, which deliver 3.3v, 5v and 12v to devices:
