Why does the fitter error happen with the message of can't read "rx1_clkout_H" while running a parallel loopback with the external VCXO design example of the GTS SDI IP generated by a former Quartus® version than 25.3? - Why does the fitter error happen with the message of can't read "rx1_clkout_H" while running a parallel loopback with the external VCXO design example of the GTS SDI IP generated by a former Quartus® version than 25.3? Description Due to some changes in the Quartus® Prime Pro Edition software version 25.3, you may see the following error while running a parallel loopback with an external VCXO design example of the GTS SDI IP generated by a former Quartus version other than 25.3. Error: can't read "rx1_clkout_H": no such variable This problem occurs because some pfd.sdc paths have changed in the Quartus® Prime Pro Edition Software version 25.3. Resolution To work around this problem during design migration from the former Quartus® Prime Pro Edition software version to version 25.3, modify the pfd.sdc file located in rtl/loopback/pfd/ directory. Changed the following lines: From : if { [string match " *profile0* " \$rx_clkout] } To : if { [string match "* prof0* " \$rx_clkout] } A parallel loopback with an external VCXO design example that has been generated in Quartus® Prime Pro Edition software version 25.3 is not affected by this problem. Custom Fields values: ['novalue'] Troubleshooting 15018351295 False ['SDI II IP'] ['FPGA Dev Tools Quartus® Prime Software Pro'] 25.3 25.3 ['Agilex™ 5 FPGAs and SoCs'] ['novalue'] ['novalue'] ['novalue']