Advantech ASMB-823I User Manual page 56

3.2.2.6 CSM Configuration
 CSM Support
Enables or disables UEFI CSM (Compatibility Support Module) to support a leg-
acy PC boot process.
GateA20 Active

This items is useful When RT code is executed above 1MB. When this it's set as
"UPON RQUEST", GA20 can be disabled using BIOS services. When it's set as
"Always", it does not allow disabling GA20.
 Option ROM Messages
"Force BIOS or Keep Current" to set the display mode for Option ROM
ASMB-823I User Manual 46