EVGA 160-LF-E659 - Manual (Page 30)

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CPU VCore Booster
For convenience of users when overclocking, the ECP houses 3 CPU Vcore
Boosters for real-time boost of CPU VCore upwards of +0.1v per button.
The Red LED will light up when VCore booster is pressed. When one Red
LED is lit, VCore is boosted by +0.v. When 2 Red LEDs are lit, VCore is
boosted by +0.2v. To stop the VCore boost, just press again and VCore will go
down to what you have set. The 2 buttons are exactly the same in function each.
Vtt Booster
The far right button on the EVGA ECP increases the VTT voltage by +0.1v.