Above 4G Decoding; Launch Storage Oprom Policy - ASROCK B550AM Gaming User Manual

Fast Boot
Fast Boot minimizes your computer's boot time. In fast mode you may not boot
from an USB storage device.
CSM (Compatibility Support Module)
CSM
Enable to launch the Compatibility Support Module. Please do not disable unless
you're running a WHCK test.

Above 4G Decoding

Enable or disable 64bit capable Devices to be decoded in Above 4G Address Space
(only if the system supports 64 bit PCI decoding).
Launch PXE OpROM Policy
Select UEFI only to run those that support UEFI option ROM only. Select Legacy
only to run those that support legacy option ROM only. Select Do not launch to not
execute both legacy and UEFI option ROM.

Launch Storage OpROM Policy

Select UEFI only to run those that support UEFI option ROM only. Select Legacy
only to run those that support legacy option ROM only. Select Do not launch to not
execute both legacy and UEFI option ROM.
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