For more details about frequencies, see the appropriate FPGA data sheet:
•Virtex-7 FPGAs Data Sheet: DC and Switching Characteristics (DS183) [Ref 1]
•Kintex-7 FPGAs Data Sheet: DC and Switching Characteristics (DS182) [Ref 2]
•Artix-7 FPGAs Data Sheet: DC and Switching Characteristics (DS181) [Ref 5]
•Zynq-7000 SoC Data Sheet: DC and Switching Characteristics (DS191) [Ref 6]