The following answer record discusses a known issue for the 13.3 version of the Virtex-6 GTX IBERT core. The "ml605 bank113fmchpc" board configuration setting sets the wrong refclk which needs to be modified by the user for a proper design to be generated for the ML605 board.
If the "ml605 bank113fmchpc" board configuration setting is used in the Virtex-6 GTX IBERT core in 13.3, a modification will need to be made to generate a working design.
In the IBERT Wizard, select the "ml605 bank113fmchpc" board configuration setting. Press "next" to get to page 4. The REFCLK sources are currently set to "MGTREFCLK0 113", change this setting to MGTREFCLK0 114. This change is necessary because the bank for the MGT has to borrow the refclk from the adjacent QUAD. No other changes are necessary to generate a working IBERT design.
This is a known issue in 13.3 and is scheduled to be fixed in 13.4.