Asus P8H77-M PRO - Manual (Page 40)

2-20 Chapter 2: Hardware information
Chapter 2
4. GPU Boost LED
The GPU Boost LED lights up when the GPU Boost switch is changed to Enable.
P8H77-M PRO GPU Boost LED
P8H77-M PRO
GPU_LED
3. EPU LED
The EPU LED lights up when the EPU switch is changed to Enable.
P8H77-M PRO EPU LED
P8H77-M PRO
EPU_LED