identified to the system by the placement of a jumper across a specific set of
pins. A jumperis a small speck of plastic with a metal strip that connects the
pins to which it is attached; it serves the same purpose as a switch. When it
is in place between two pins, that particular circuit is completed; when it is
absent, that circuit is open or disconnected.Even though the hard drives produced for laptops are considerably smaller
than those made for desktop machines, they follow the same technical and
electrical specifications as their larger cousins. In theory, a 2.5-inch hard
drive can be adapted to work in a desktop or tower PC and if it were attached
to an IDE cable with two devices — two hard drives or a hard drive and CD
or DVD drive, for example — one of the devices would have to be identified
through the use of jumpers as the master and the other as the slave.But let me get back to laptops, for that is the purpose of this book — it says
so right there on the cover. Very few laptops have more than one internal
hard drive, and the drive bays are directly connected to the motherboard’s
hard drive controller by a cable that makes no provision for a second device
on the same link.Helping you out a bit more, most hard drive manufacturers ship their equip-
ment with a default setting as the master device. Check the instruction
manuals that come with a new drive or consult the Web sites for advice
about the need to make any changes in jumpers.If your laptop does, in fact, allow for a second hard drive — some machines
offer an extra bay that can be used for a hard drive, a floppy disk drive, a CD
or DVD drive, or even be convertible to hold an auxiliary battery — consult
the instruction manuals or call customer support to determine how that bay
is electrically configured. It might require configuring the additional drive as
a slave device (requiring you to set jumpers accordingly) or it may be con-
nected to the motherboard by a separate IDE channel and devices installed in
that bay may be considered master devices on a second channel. Once you
find the answer, the only instance in which you are likely to have to make a
change to jumper settings is if the device will be set up as a slave.Like I said about that monkey in a change of dress, when it comes to setting
jumpers, no two hard drives are going to be exactly the same. However, they
are going to be very similar. In Figure 7-3 is a diagram of the back end of one
typical hard drive.As you can see, four pins at the right side (as you face the connector) are
marked A, B, C, and D. The jumpers can only be installed horizontally or ver-
tically, and not on a diagonal. This allows the following jumper connections:
AB, AC, CD, and DB. (Some drive makers also allow for settings based on two
jumpers, which makes for a fifth jumper condition: AC plusDB.)132 Part III: Laying Hands on the Major Parts