In Virtex-6 FPGA instances of the XAUI v9.1 core using the 32-bit XGMII interface, the MMCM parameter values used in the example design will result in an MMCM VCO frequency that is below the newly specified minimum.
This will result in DRC failures in the next release of ISE Design Suite.
For more details on the MMCM issue, see (Xilinx Answer 33849).
Depending on how the core was configured at generation time, there could be zero, one, or two instances of the MMCM in the example design.
Each of the MMCM parameter values should be changed as follows:
CLKFBOUT_MULT_F: from 3.0 to 6.0
CLKOUT0_DIVIDE_F: from 3.0 to 6.0
CLKOUT1_DIVIDE: from 3 to 6