Asus M4A89GTD PRO Supplementary Manual page 21

COM Port
Note: This is an auto test.
Serial Port Test items:

Loopback Test
After setting the Serial Port to the Loopback mode, tests the stability of the Serial Port
with different baudrates including 115200 bps,57600 bps,38400 bps,19200 bps,9600
bps,4800 bps,2400 bps, and 1200 bps.
Note: The actual max. test baudrates vary with devices.

Control Pins Test
Tests if the signal status of pins of the Serial Port are correct.
Note: If the current Serial Port is in use, it can not be tested. Please remove the device from
the Serial Port before testing.