Shuttle P20U Bios Manual page 20

Boot from USB device
Enabled/Disabled onboard USB storage boot function.
 The choice: Enabled, Disabled.
Boot from Card-Reader
Enabled/Disabled onboard Card-Reader boot function.
 The choice: Enabled, Disabled.
Boot Mode Select
Choice Boot ro UEFI or Legacy.
 The choice: LEGACY, UEFI.
Boot Device Priority (Boot Option #1/2/3/....)
Specifies the boot sequence from the available devices. A device enclosed in
parenthesis has been disabled in the corresponding type menu.
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