Aaeon PCM-4894 User Manual page 46

Gate A20 Option
This entry allows you to select how gate A20 is handled. Gate
A20 is a device used to address memory above 1 MB. Initially,
gate A20 was handled via a pin on the keyboard. Today keyboards
still provide this support, however it is more common and much
faster for the system chipset to provide support for gate A20.
The choices are thus: Normal and Fast.
Security Option
This category allows you to limit access to the system. The
choices are System: which requires a password at boot up and
Setup: which only requires a password to access the setup utility.
Video BIOS Shadow
Determines whether the video display card BIOS will be copied
into system DRAM in order to increase display speed and is
required for system performance. However, it is optional
depending on the chipset design. The default setting is Enabled.
Shadowing Address Ranges
The next 3 lines, from C8000-CBFFF Shadow to DC000-DFFFF
Shadow are address ranges for shadowing other expansion card
ROMs. If there are any expansion cards with ROMs installed in
your system, you have to know the address range they use in order
to shadow them specifically. The default setting for all of these is
Disabled.
40 PCM-4894 User Manual