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First off I would like to thank [-elmo-] for his suggestions for doing this mod.
SATA power to Molex cable
XBOX 360 SATA HDD removed from its case
Solder iron (I used a 15/30 watt from radio shack)
some items you might need:
^^I used these for extending wires and covering exposed wire with hotglue and electrical tape.
SATA Power Cable to Molex cable and generic SATA cable. On my Sata power cable there was a yellow cable(12V) and another black cable(ground) you can just cut those right off at the connector.
First you need to decide where you are gonna place your HDD, you can prob put it on the opposite side of the case if you wanted to, you might just have to extend the some cables. You might be able to put the harddrive under the opposite grill, above the shielding and below the grill, this may require you to cut some metal shielding to place it there. For me, I am just resting it on my DVD drive.
My length will be short, just enough to make it above the DVD drive and connect the HDD. Cut your wires to the proper length and strip the wires.
Here's a picture of the SATA connector that shows numbers that correspond to the pins on the motherboard. Make sure you follow the wire from the pin on the connector to the end of the wire you stripped, as it is important to where you connect to on the motherboard.
There is 7 total wires in the SATA cable. Wire 7 which corresponds to pin 7 on the motherboard, is right next to the L shaped part of the SATA connector. When I stripped mine, some of the wires were already exposed and not shielded, so I didnt want that to be a problem with anything so I took some wire and soldered 7 pieces to the SATA cable so no wire would be exposed to touching metal. I then covered the wires in hot glue and then covered those in electrical tape. I didnt want any shorts to happen or any damage to the mobo or HDD to happen.
Next you want to locate the pins under the motherboard. They are directly below the HDD connector on the motherboard. I numbered all the pins accordingly and will tell you each pins function.
Pins 1-7 are for the SATA cable
Pins 8-10 are ground
pins 11-13 are 5V
pin 14 isnt used.
Now you want to solder your SATA data cable to the bottom of your motherboard. Make sure you connect the correct wire to each pin. You will be using pins 1-7, see picture below.
Now after you solder the SATA data cable, you need to solder your SATA power cable. The wire gauge was to fat on my power cable, so I soldered a smaller gauge wire to it so I could connect to the pins easier. You can use pins 8-10 for ground and pins 11-13 for power. I used pin 10 for my ground and pin 11 for my 5V power connection. You only have to connect to one of these pins, perhaps you could use this 5V for a LED mod or something in the future, which I will be. Solder your ground to pin 10 and solder your 5V to pin 11 and you are almost done.
Cover your solder work with hot glue or electrical tape. Place your HDD where you plan on having it and connect your wires and you are done. Test to make sure your HDD works before putting everything back together first.