The equalizer DC gain selections in Quartus® II software version 7.2 or earlier Megawizard are 0 (0dB), 1 (3dB) and 2 (3dB).
To set 6dB equalizer DC gain, modify the parameter for DC gain in the ALT2GXB wrapper file and set it to 6dB. You can also set it to 6dB (rx_eqdcgain = 11) by using dynamic reconfiguration feature.
Change the following parameter in the wrapper file generated by the Megawizard:
alt2gxb_component.equalizer_dcgain_setting = 3,