Asus P8P67 WS Revolution - Manual (Page 39)

2.2.6 Onboard LEDs
1. POST State LEDs
POST State LEDs check key components (CPU, DRAM, VGA card, and
HDD) in sequence during motherboard booting process. If an error is found,
the LED next to the error device will continue lighting until the problem is
solved. This user-friendly design provides an intuitive way to locate the root
problem within seconds.
You may disable the POST State LEDs in BIOS. Refer to section 3.7.2 Boot
Setting Configuration for details.
2. TPU LED
The TPU LED lights when the TPU switch is turned to Enable.
ASUS P8P67 WS Revolution 2-13