SATA power

Question

Just a learning question.   Are there any SATA HD's or opticals (DVD burner, etc) that require or use the 3.3v orange wire on a normal SATA power plug? I see plenty of 4 pin molex Y splitters but when I look for the same in a SATA configuration, all I see is one or two SATA plugs that connect to a 4 wire molex.... ie, no orange wire hookup. The only thing I can find on web searches seem to be articles that are several years old saying 3.3v isn't necessary but they obviously aren't addressing newer devices; 2006 or later. I didn't know if anything has changed since SATA came out. And if you don't need the 3.3v, why is it there?   Thanks,   Ken

x_lab rat · Answer

Explain the 3.3V standard? I wasn't even aware such thing existed. Not disputing that it does/could exist, just that the standard distribution voltages have kinda boiled themselves down to 12 and 5. If 3.3 were needed specifically it could readily be derived from the existing standards.

The core voltage standard at one time was 5V. Virtually all digital logic ran on it. We'd still be on that standard--awesome noise immunity--were it not for dissipation/sq. in. increasing so dramatically with speed and density. We're at well-under half that today. And it's derived from the 12V standard, which at one time ran only motors (fans, drives) and a few analog audio/video amps.

I can only guess that the SATA-standard guys were thinking futuristically, to where 3.3V was a logic standard like 5V was since 1970. But since commodity power supplies don't generally support 3.3V, if a SATA drive really needs 3.3V it had better be equipped to produce it itself from either 5V or 12V.

There may be a much more substantive explanation, in which case I'm flaunting my ignorance. Willing to take that risk for the sake of lively exchange.

Message Edited by x_lab rat on 04-17-2007 05:03 PM

x_lab rat · Answer

Well mate, you put me to shame.  I purport to have been 'in the industry' but I have yet to see an orange wire in the drive power breakout.  (I was there through the introduction of the current Dimension chassis.)  Then again, busy as I was, if there was never a 3.3V issue I might well not have noticed there was a 3.3V rail.  Can't see a point to it, considering the ease with which 'standard' voltages are downconverted (with a current advantage) at the load point (load-point regulation is ideal).   Don't tell me I'm the most knowledgeable desktop engineer here.  Please.  Somebody straighten us out.  I can't stand the pressure.  :smileywink:

kdmphx · Answer

For some reason, I thought you'd be the one to answer. Thank you.   I just thought it was strange that when you look at a SATA plug on a PSU wiring harness, it has an orange 3.3v wire attached, yet anytime you looked at either a Y splitter or extension for a SATA plug, it shows it being attached to (made from) a standard 4 pin molex, 12V connector, 4 wires ... no orange wire. I figured it wasn't necessary so applying too much logic, I was trying to come up with a reason why they manufactured it that way when attached to a new PSU wiring harness????    Like you said, maybe they thought they'd need it when the standard was first developed. But foolish me, I thought if it wasn't necessary, it wouldn't still be coming that way on new PSU's, so obviously, it must be necessary for something.   Ken

kdmphx · Answer

Here's a picture...

Ultra Quiet Silencer 470 ATX Power Supply

And this from wikipedia.. http://en.wikipedia.org/wiki/Serial_ATA

The SATA standard also specifies a new power connector. Like the data cable, it is wafer-based, but its wider 15-pin shape prevents accidental misidentifcation and forced insertion of the wrong connector type. Native SATA devices favor the SATA power-connector over the old four-pin Molex connector (found on all PATA equipement), although some SATA drives retain older 4-pin Molex. The SATA/power connector has been criticized for its poor robustness -- the thin plastic tops of the connectors (see power connector picture at right) can break due to shearing force when the user pulls the plug at a non-orthogonal angle. The seemingly large number of pins are used to supply three different voltages: 3.3 V, 5 V, and 12 V. Each voltage is supplied by three pins ganged together, 5 of the remaining pins 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.

Color Function Yellow +12 V Black Ground Red +5 V Black Ground Orange +3.3 V

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. However, without 3.3 V power, the SATA device may not be able to implement hotplugging as mentioned in the previous paragraph.

Message Edited by kdmphx on 04-17-2007 06:44 PM

Message Edited by kdmphx on 04-17-2007 06:44 PM

x_lab rat · Answer

And the lights came on all over the world. Well, you don't know something until you do. As many SATAs as I handled and I never noticed an orange wire? Could Dell have specified their SATAs ran on 12V and 5V because that's what their PS vendors were already making? While the rest of the industry did something else? And SATA drives sometimes included the PATA power option (Molex, 12V, 5V, ground). Entirely possible, all of those.

My only excuse can be that it was never an issue with Dell desktops, or I would have been aware of it.

So we still need an answer. Anyone?

Message Edited by x_lab rat on 04-17-2007 07:38 PM

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SATA power

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