Asus Z97-A/USB 3.1 User Manual page 47

3. TPU LEDs (TPU_LED)
The TPU LEDs light up when you set the TPU switch to TPU_I mode or TPU_II mode.
4. EPU LED (OLED2)
The EPU LED lights up when the EPU switch is enabled.
ASUS Z97-A/USB 3.1 1-37