For the Reference Clock, check the following section of the User Guide.
(Reference) Intel® Stratix® 10 L- and H-Tile Transceiver PHY User Guide
https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/stratix-10/ug_stratix10_l_htile_xcvr_phy.pdf
- 1.3.5.2. Input Reference Clock Sources
- 3.2.
Also, please actually create a sample with Quartus® Prime, place the terminals and check if it is possible to place them.
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Category: PCI-Express
Tools: Quartus® Prime
Devices: -