altera_internal_jtag clock and timing issues

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I am in need of higher clock more than 600MHz.... In Altera Fpga kit it has an internal clock upto 50Mhz. If i use any external clock source, which is going to be compatible? function generator or crystal oscillator. Is Crystal oscillator alone is enough to form the external clock.

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Why do You need such fast clock? Dream on about having such on FPGA itself. You can only get such fast clock on transceiver block. Check Your FPGA datasheet for Fmax.