Asus Maximus IV Extreme-Z - Manual (Page 55)

8. Power LED
The motherboard comes with a power-on switch that lights up to indicate
that the system is ON, in sleep mode, or in soft-off mode. This is a reminder
that you should shut down the system and unplug the power cable before
removing or plugging in any motherboard component. The illustration below
shows the location of the onboard power-on switch.
7. Q LED
Q LEDs check key components (CPU, DRAM, VGA card, and booting
devices) in sequence during motherboard booting process. If an error is
found , the corresponding LED will continue lighting until the problem is
solved. This user-friendly design provides an intuitional way to locate the root
problem within a second.
ASUS Maximus IV Extreme-Z 2-23