Epson 486SX - Manual (Page 125)

You can install drives in the internal bays. In the
external bay, you can install drives or drives
with mounting frames attached.
You also need to attach metal drive brackets to each drive you
install in the external bay. Two sets of these brackets (with
retaining screws) come in the box with your computer. The
instructions in this chapter tell you how to install them.
Setting the IDE Hard Disk Drive Jumpers
You may need to change the hard disk drive jumper settings if
you install or remove an IDE hard disk drive. The jumpers tell
the computer whether you are using one hard disk drive or two.
Note
You do not need to set any jumpers if you are removing
your only hard disk drive.
If you are installing only one hard disk drive, see “Changing
the Jumper Settings” below to check your drive’s jumpers.
If you are removing one hard disk drive and leaving another in
your computer, you need to change the jumper settings on the
remaining drive to indicate that it is the only hard disk drive
installed.
If you install two hard disk drives, you must change the jumper
settings on each drive to indicate whether it is the master
(primary) or the slave (secondary) drive. The primary drive is
the one from which you boot your computer.
Installing and Removing Drives 7-3