Epson Endeavor - Manual (Page 99)

2. Locate the hard disk drive ribbon cable. If you are installing a
second hard disk drive, one end of the cable is connected to
the system board and the other end is connected to the first
hard disk drive in the vertical drive bay; use the free middle
cable connector to connect the second hard disk drive as
described below.
If you are installing your computer’s first hard disk drive, you
need to connect the hard disk drive ribbon cable to the
system board now. Follow the instructions on page 3-33
and then use the middle cable connector to connect the hard
disk drive as described below.
Notice the small tab in the middle of the cable connector;
align this tab with the notch in the hard disk drive
connector, as shown below.
3-26 Installing and Removing Drives