To determine what clock resources are being used, refer to the Clock Report which is found in the place and route report ("*.PAR"). Below is an example:
------------------ Clock Report ------------------
Global Clock Resources: CLK_PIN : 1 out of 6 (16%)
PLL : 0 out of 10 (0%)
DCS : 0 out of 8 (0%)
Quadrants All (TL, TR, BL, BR) - Global Clocks:
PRIMARY "clk_c" from comp "clk" on CLK_PIN site "C12 (PT76A)", clk load = 12
PRIMARY : 1 out of 8 (12%)
DCS : 0 out of 2 (0%)
DCC : 0 out of 6 (0%)
SECONDARY: 0 out of 8 (0%)
Edge Clocks: No edge clock selected.
Regional Secondary Clocks: No regional secondary clock selected.
--------------- End of Clock Report ---------------