Advantech ASMB-260T2-22A1 User Manual page 42

3.2.2.9 CSM Configuration
 CSM Support
Enable or disable UEFI CSM (Compatibility Support Module) to support a leg-
acy PC boot process.
GateA20 Active

This item is useful when RT code is executed above 1MB. When it's set as
Upon Request, GA20 can be disabled using BIOS services. When it's set as
Always, it does not allow disabling of GA20.
ASMB-260 User Manual 36