In a design that includes a 1000BASE-X/SGMII PCS function
and targets a Cyclone IV GX device, the REFCLK used
for the 1000BASE-X/SGMII PCS function do not have access to GCLK
network. When you compile the design in the Quartus II software,
the Fitter module cannot fit the design and reports an error.
This issue affects all designs that include 1000BASE-X/SGMII PCS functions and target Cyclone IV GX devices.