
For some older Intel RAID controllers, and others, that are limited to SATA 150, this setting applies.
But for newer SATA 300 RAID controllers as well as onboard SATA 300 controllers this jumper should be removed in order to obtain the performance that the hard drive was designed for.
A label on top of the drive indicates this:

Philip E.
MPECS Inc.
Microsoft Small Business Specialists.