Asus Maximus III Extreme - Manual (Page 33)

4. Hard Disk LED
The hard disk LED is designed to indicate the hard disk activity. It blinks when
data is being written into or read from the hard disk drive. The LED does not
light up when there is no hard disk drive connected to the motherboard or
when the hard disk drive does not function.
5. BIOS LED
The BIOS LEDs help indicate the BIOS activity. Press the BIOS button
to switch between BIOS1 and BIOS2 and the LED lights up when the
corresponding BIOS is in use.
ROG Maximus III Extreme 2-3