Asus P8Z77-V PRO/THUNDERBOLT - Manual (Page 86)

3-14 Chapter 3: BIOS setup
Chapter 3
DRAM DATA REF Voltage on CHA [Auto]
Allows you to set the DRAM DATA Reference Voltage on Channel A/B. The values
range from 0.395x to 0.630x with a 0.005x interval. Different ratio might enhance DRAM
overclocking ability.
DRAM CTRL REF Voltage on CHB [Auto]
Allows you to set the DRAM Control Reference Voltage on Channel A/B. The values
range from 0.395x to 0.630x with a 0.005x interval. Different ratio might enhance DRAM
overclocking ability.
CPU Spread Spectrum [Auto]
[Auto] Automatic configuration.
[Disabled] Enhances the BCLK overclocking ability.
[Enabled] Sets to [Enabled] for EMI control.