You may see the above error when generating a Stratix IV DDR3 UniPHY controller in the Quartus® II software version 13.1 or later. There is a new frequency check in the MegaWizard Plug-in Manager IP GUI that prevents users from running the interface faster than the maximum supported frequency. If you specify the maximum supported frequency with more than 3 decimal places (i.e. 533.3333MHz), it will lead to the above error.
Device Family: Stratix® IV E, Stratix® IV GT, Stratix® IV GX
Area: EMIF, Intellectual Property
IP Product: DDR3 SDRAM Controller MegaCore supporting UniPHY
The workaround is to limit the DDR3 Memory clock frequency in the PHY Settings tab of the MegaWizard™ Plug-In Manager to three decimal places.