Keyword: architecture, DCM, high, frequency, period, DLL_FREQUENCY_MODE, HF, LF, DRC
When I select "CLK2X" in the Board De-skew flow of the Clocking Wizard, the 2X clock is not restricted in the low-frequency mode range. This should be restricted by the DRC, because CLK2X can only be used in the low-frequency range.
This problem has been fixed in the latest 6.1i Service Pack, available at:
The first service pack containing the fix is 6.1i Service Pack 1.