Description
You might see the above Fitter error in Quartus® Prime software version 15.1 with Stratix® V and Arria V GZ devices.
The reason for the error is because the Quartus Prime software version 15.1 software fails to merge two or more ATX PLLs.
Resolution
To work around this problem, you can use Quartus Prime software version 15.1.1 or later.