Powering drives through the motherboard

[8biosdrive]

Some major computer makers have stopped supplying power directly from the power supply to internal hard drives and optical drives. Instead, the power is delivered via a connection to the board, and the devices draw their power from SATA power sockets on the board. What are the advantages of doing this? Isn't one disadvantage that over time the board circuits could be stressed, resulting in some failure? Or is this not a problem?

[robertferanec]

Please, can you attach some pictures?
I have not noticed this. But it has been couple of years now when I was buying a new computer .. so who knows. However, I do not really see reasons why it should change.

[8biosdrive]

Here are two pictures of the insides of a new Dell Inspiron 3670 desktop. In the bottom picture you see the cables coming from the power supply. There are two bundles; the larger bundle connects to the 4x4 pin white connector at the upper right corner of the board, which is labeled "ATX SYS" (shown closer-up in the top picture).

The second bundle of 2 yellow and 2 black wires connects to a white 2x2 connector (partially obstructed by the blue data cable in the bottom picture) and then goes around the chasis to a 2x2 white connector which connects to the board and is labeled "ATX CPU" (not shown). There are no SATA connectors coming out of the power supply.

In the bottom picture you can see 5 black wires bringing power to the hard drive from the SATA power 3x3 black connector in the board (seen in the bottom picture and in close-up in the top picture). I added a solid state drive, which received power from a cable which attached to the unoccupied black SATA power connector in the upper picture. This design was used in two earlier models of the Inspiron, and in some earlier models of the Vostro and OptiPlex desktop series. I'm not sure if only Dell powers devices from the board, or if other computer manufacturers are doing the same.

[Paul van Avesaath]

looks too me as a feature for thin clients.. then youd ont have to have a bulky power supply in there.. easier cable managment?

[robertferanec]

I also think it may be something special, not really a standard.

[8biosdrive]

I also think it may be something special, not really a standard.

Understood. So why would Dell take this approach to powering devices through the motherboard? The power supply is rated for a relatively low 290 watts. Does this design allow for a cheaper power supply to be used? And what is the long term effect on the board circuits?

[Paul van Avesaath]

a psu for a Sata drive is not that difficult or expensive, so why not.. you can have a 5V and 3.3V with 2A output current for around 1$ or less if you go into bulk production..
long term effects.. who knows.. I would not worry about it. there is nothing special about a PSU like this..

also the enviroment where it is placed is nothing special either..

so it should work longer than the sata drive it is suppose to power

and yes looking at you pictures it probably reduces the cost of the PSU (which is probably something they do not develop themselves, so they have to buy it)
a single 12V PSU is much cheaper than a atx psu..

do you have a picture of the connection from teh psu to the motherboard?

[robertferanec]

do you have a picture of the connection from teh psu to the motherboard?

I think, PSU could be in the bottom right corner (second picture) ... only a few wires

[8biosdrive]

so it should work longer than the sata drive it is suppose to power

and yes looking at you pictures it probably reduces the cost of the PSU (which is probably something they do not develop themselves, so they have to buy it)
a single 12V PSU is much cheaper than a atx psu..

do you have a picture of the connection from teh psu to the motherboard?

There are two connections from the power supply to the motherboard. The white 4x2 connector shown in the upper picture in the upper right hand corner of the board is labeled "atx sys" and there is a 2x2 connector in the lower left hand corner of the board (not shown) labeled "atx cpu." My concern isn't so much for the psu as for the longevity of the board circuits. In a more typical design, the current is going directly to the drives, not through the board.

[robertferanec]

So why would Dell take this approach to powering devices through the motherboard?

- Maybe they do not want to be compatible? Maybe the PC is small and they had to go for a non standard solution? I am not sure what could be their reason.

[Paul van Avesaath]

could also be that they did it so that service parts would be unique to dell support and thus would be a money maker for them in the long run..