Due to a problem in the Quartus® II software version 13.1 and earlier, you may see that your Arria® V design fails to route when the device is not fully utilized. This problem occurs when a high fanout clock is incorrectly promoted to a regional clock net that restricts the placement of the destination logic to a quadrant of the device.
To work around this problem, manually assign your clock to be global rather than regional using the assignment below:
set_instance_assignment -name GLOBAL_SIGNAL "GLOBAL CLOCK" -to "<clock name>"
This problem is scheduled to be fixed in a future version of the Quartus II software.