Xbox 4 Connector IDE cable UDMA ATA 100
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This tutorial was written based on one of our older cables that we hand made we are now offering .  Installing this cable does not mean you get to have two hard drives at the same time, it does mean you can quickly choose between one drive and another with greater ease, simply provide power to the drive that you want to use and do not provide power to the drive you are not using.  

Notice how each connector is labeled in this picture?  They are all wrong!  It would have been slick to have the DVD be the connector next to the CPU board connector, (less folding to get a proper fit!)  Turns out that the only way this works is to connect the one labeled Master to the motherboard, the one labeled Slave to the DVD and the ones labeled DVD and CPU Board to the hard drives.  

Start with the end with the black connector, this is the end that will be attached to the motherboard, feed the entire cable through the black loop.

Once this is complete the IDE cable extends from the same side as the keyed side of the black connector rather than the opposite side as before.  Once the cable is folded over the top of the black connector and going in the same direction as the keyed site, make a 90 degree fold about one inch from the black connector, this will send the cable in the direction of the DVD drive.  Now the keyed side of the gray connector must be facing up so again fold the cable around the connector as on the black one, this leaves the remainder of the cable heading downward rather than toward the Hard drive. 

Make two more 90 degree folds right below the gray connector, this will send the cable up past the DVD drive, you can then make two more that will end up being on top of the DVD drive, this sends the blue connector to the hard drive.

When you are done it should look something like this.  (in the photo the cable is pointing up and it may look like there is not enough space to be able to connect a hard drive to the blue connector and have the drive laying on top of the Xbox I assure you there is)

Power Splitter cable-

Start with the following components

Power Splitter

DPDT Switch

Begin by snipping the red and yellow wires about one inch from the connector that has dual wires coming out of it.  Then clip one of the two wires as close to the base as possible, notice there is only one yellow wire and a nub, do the same to the red. Strip all ends about a 1/16 of an inch, just enough to make contact on the switch.

The one inch wires that go from the connector go to the long pins in the middle of the switch, note that there are 3 yellow on one half of the switch and the 3 red on the other half.  Both yellow are red wires for IDE1 are on the left and both yellow and red for IDE 2 are on the right. 

A few notes on two position DPDT (dual pole dual throw) ON/ON switch.
Dual pole means there are two separate circuits in this switch (1,2,3 is one 4,5,6 is the other) 
Dual throw means that both circuits are flipped simultaneously.   
Two position means there are two positions the switch can be in.   
ON/ON means that when flipped in either position a circuit is on.

Lets talk about the yellow wires 4,5,6.  When the switch is in one position 5 makes contact with 4, when in the other position 5 makes contact with 6.  The same holds true on the other half of the switch so when in one position both 2 and 1 make contact and at the same time 4 and 4make contact (they do not cross over ie 4, 5, 6 does not contact 1, 2, or 3)

Well that's about it, mount it so the switch is protruding out the back. Only switch from one drive to the other while the Xbox is powered off.