Acer 240 - Manual (Page 58)

2 Customizing my computer 50
Englis
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Primary Master
The Primary Master sub-menu contains parameters related to the hard
disk installed in your computer.
Caution: The parameters in this screen are for advanced uses only.
Typically, you do not need to change the values in this screen. The
default setting of Auto optimizes all the settings in your hard disk
drive.