Acer AcerAltos 21000 System Manual page 111

Serial Port 2
This parameter allows you to enable or disable the serial port 2. The
Base Address and IRQ items are configurable only if this parameter is
enabled.
This function lets you set a logical base address for serial port 2. The
options are:
3F8h
2F8h
3E8h
2E8h
This function lets you assign an interrupt for serial port 2. The options
are IRQ 3 and 4 .
BIOS Utility
Base Address
IRQ
If you assign 3F8h to serial port 1, you may only
assign 2F8h or 2E8h to serial port 2.
If you assign 2F8h to serial port 1, you may only
assign 3F8h or 3E8h to serial port 2.
4-25