Epson Progression U12 - Manual (Page 107)

Checking the IDE Hard Disk Drive Jumpers
IDE (Integrated Drive Electronics) hard disk drives have
jumpers that must be set for the drive to work properly with
your computer. The jumpers tell the computer whether you are
using one hard disk drive or two. If you purchased your system
with a hard disk drive already installed, these jumpers have
been set for you. You may need to change the jumper settings if
you install or remove a hard disk drive.
Note
You do not need to set these jumpers if you are removing
your only hard disk drive.
Check the jumper settings if you are doing any of the following:
Installing your first hard disk drive
Removing one hard disk drive and leaving another in your
computer
Installing a second hard disk drive.
See the documentation that came with your hard
disk drive
for
the proper settings. If you install two hard disk drives in your
system, you must change the jumper settings on each drive to
indicate which drive is the master (primary) drive and which is
the
slave (secondary) drive.
A master drive is the drive
on which
you’ll install the operating
system that the computer loads into its memory each time you
turn it
on.
You can run application programs and store data on
both the master and slave drive, but the operating system must
be contained on the master drive.
4-4 Installing and Removing Drives