Some SATA drivers have jumpers for extra features, or for troubleshooting.
Example from the manual of a Western Digital SATA disk:
Set the Jumpers
The default setting for WD SATA hard
drives varies depending on the model.
To determine the default setting for
your drive, look at the drive label on
the top of the drive.
DO NOT change
the default setting if you intend to
use the drive in a desktop computer.
Change the jumper settings ONLY if you
intend to use the drive in an
enterprise storage environment. For
more information on these advanced
settings, obtain the full version WD
SATA Installation Guide at
(Default) — Enable or disable the
spread spectrum clocking feature.
Default setting is disabled.
OPT1 — Only for factory use.
OPT2 — Only for