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SATA power connecters hae extra wire... what for?

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January 15, 2007 7:40:17 PM

SATA power connectors have an extra 3.3v(?) connector...
what is it used for considering that hardrives seem to work fine without them... (using standard molex connector to SATA converter cable)

is there any benifit to using power that has the extra wire on it?
January 15, 2007 8:28:27 PM

I have no idea what you are talking about... where is the extra wire?
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January 15, 2007 11:24:29 PM

12v
gnd
5v
gnd
3.3v

wonder if its because the 12v has its own ground and the 5th wire is the combined ground for both the 5v and 3.3v?

otherwise you would have 18.3v on one ground.
January 16, 2007 12:48:33 AM

Don't think you can add up the voltage up like that to get 18.3v
you can add negative voltage and positive voltage together to create a larger difference.. but all positive voltage can be added up like that..

as for the 3.3v i don't know why it is there...
I have 9 HD's in my machine and only one of them is using the SATA power connector from my PSU with the 3.3v on it,..
the rest are using standard molex to sata power converter...

I'm just wondering what the 3.3 volt line is for since not having it doesn't seem to affect the functionality of my drives...
January 16, 2007 1:11:59 AM

SATA provides the 3.3V power to those hard drives that want to use it. If the hard drive uses 3.3V components on board (most do), there is no need to provide 5V->3.3V conversion circuitry on the hard drive circuit board, reducing the component count and cost.

However, hard drive manufacturers have been reluctant to rely on the presence of the 3.3V line, since when a molex->SATA power converter cable is used, the 3.3V power is not available. Thus, most hard drives use 5V/12V power exclusively, and create their own 3.3V power on board.

The ground lines are common to all power rails. Voltage is not added or subtracted like that, voltage is a measure of how positive or negative the line/pin is held at by the power supply. Ground lines are held at ground potential, i.e. 0 V. Current sourced from any power line is returned to the power supply through the ground lines. Multiple ground lines are used to a) handle the total maximum current flow (it is typically higher than what is considered maximum for the small individual contacts in the SATA connector), and b) multiple ground lines that lie in between the power lines decouple any noise from one power line to the next, providing noise rejection.
January 16, 2007 1:29:28 AM

Thanks... that answered my question nicely
August 26, 2012 11:58:41 AM

MadHacker said:
SATA power connectors have an extra 3.3v(?) connector...
what is it used for considering that hardrives seem to work fine without them... (using standard molex connector to SATA converter cable)

is there any benifit to using power that has the extra wire on it?


the extra is the orange witch is 3.3v your hard drive will convert 5v to 3.3 internally thats why you see adapters with out the orange wire . hope that answered your question. Kevin
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