How does a Motherboard SATA header provide power to a front eSATA port?

If you plug the cable into one of the SATA headers for the Data Transfers... that port should also have a secondary cable that supplies power to the eSata Port. Just trace the cable that leads up to the port and that is the one you plug into your PSU.

If you plug the cable into one of the SATA headers for the Data Transfers... that port should also have a secondary cable that supplies power to the eSata Port. Just trace the cable that leads up to the port and that is the one you plug into your PSU.

that is only eSATAp not that widely used. the plug on eSATAp is slightly different

eSatap? <gasp!> Some folks is been using some esoteric stuff.

Hi I recently got a case for a build and it has a front eSATA port. And of course, it has a cable inside the case to plug into one of the MOBO's SATA headers. I was wondering how an adapter cable such as the one in the link below will work to supply power to devices, since the only internal connection will be to a data transfer header.

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I don't think the eSATA input on the case is eSATAp. Here is a link to the make and model of case, in the event it could be of relevance:

http://www.newegg.com/Product/Product.aspx?Item=N82E16811121119&cm_re=HEC_6T10LITE-_-11-121-119-_-Product

OP, that case is depending on a quirk. Although there are significant differences on a few details between eSATA and "regular" SATA, many mobo makers and their chip suppliers have used SATA controller chips that actually provide eSATA specs on their "regular" SATA mobo ports. The trouble is, there's almost not way for you to confirm this for any particular mobo. So the case makers are betting that your mobo is one that does have this extra capability in its "regular" SATA ports, and maybe it does. Usually it will work but not guaranteed.

Now, the power thing. chainsaw667 has the right answer. power to the connected device never was part of the eSATA spec. ALL eSATA devices are supposed to have their own power supply. And most certainly, NO "regular" internal SATA port supplies power to the HDD it is connected to. Those ports are strictly data ports. Later a variation of the eSATA port was introduced called eSATAp that does provide limited power to the attached external device, but it uses non-standard connections and wiring. So it is VERY unlikely that your case's front eSATA port is one of these non-standard eSATAp ports.

Bottom line: just as the original eSATA spec was intended, your external eSATA device that you plug into the eSATA front port will have to have its own power supply.

By the way, that adapter cable in the link you gave is nothing like what you wanted. It is to be used IF your computer already has one of those non-standard eSATAp ports, and you use this cable from that port to plug in a SATA HDD unit. It connects both data and power links to the HDD, BUT only low-power units like the 2½" 5400 rpm units sold for use in laptops and "laptop external hard drives".

ArtPog, the description in the link says:

Description:
Power Esata port can supply 5V power to work with 2.5" Sata or SSD drive. It can support USB2.0 device to plug-and-play. Many laptops has Power Esata Port on markett now.
Please make sure your laptop is with Power Esata (Esata+USB combo) Port before bidding this item.

That says to me that this unit uses the power available from a Power eSATA port to run a 2½" SATA drive. It does NOT say it uses a standard USB2 port. The "Power eSATA" port on a computer is designed so that EITHER a USB2 connector cable OR an eSATAp cable can be plugged into it. If you look closely at the photo of the cable in the link, one end has both data and power connectors for a SATA unit (not an external enclosure), and the other end is clearly NOT a standard USB2 connector, it is an eSATAp connector. I doubt you could plug this latter connector into anything inside an external USB enclosure.

I agree, it's too bad eSATA never became as popular as USB2, because it is much better for connecting hard drives. I've always liked the concept that eSATA is just straight-through SATA over a longer cable, and does not require any protocol translation system as USB does. However, it is not much use for all the other items that use USB ports. And, of course, it never did provide power, which is just fine with me. What I find amusing is that ALL of these higher-speed interfaces (USB3, eSATA, Firewire 400 and Firewire 800) are actually limited to the speed of the HDD, which tops out at under 2 Gb/s for any mechanical HDD. Only SSD's can exceed that, and ALL of those interfaces can handle any SSD's data speed. Yet too many think that USB3 at 5 Gb/s and USB3.1 even higher will get them more speed! The only devices I can think of today and into the near future able to use a 6 Gb/s data transfer rate are multi-drive NAS units that can funnel the data for several HDD's through one cable to a computer. Such a unit connected by USB3 (much faster than Gigabit Ethernet) could be useful if the computer involved were able to keep up with it.