ASROCK IMB-1312 User Manual page 41

CSM (Compatibility Support Module)
CSM
Enable to launch the Compatibility Support Module. Please do not disable
unless you're running a WHCK test.
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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