Question related to clock resource on Stratix V GX evaluation board

The high-speed clocks on the Stratix V GX Signal Integrity Kit—those running at 625 MHz, 644.53125 MHz..... —are tied strictly to the transceiver circuits. They aren’t usable for core logic, can’t feed the main PLLs, and won’t connect through something like ALTCLKCTRL. They’re simply not wired for general use in your design. If you need a clock for your logic, you’ll have to look elsewhere—like a lower-frequency on-board oscillator (often something like 50 MHz), or bring in your own via an HSMC port or SMA connector. Just make sure the pin you use can actually connect to the FPGA’s internal clock routing.