Why does MegaWizard report the multiplier output register option is no longer available when I upgrade my multiplier to Quartus 13.1?

Description

The multiplier output register option is not available on 28nm ("V" series) devices.

Resolution

To resolve the error, disable the multiplier output register option and regenerate the core.  If you wish to preserve the original latency introduced by the register, use the Pipelining tab to add a pipeline register with 1 clock latency.

If an output register is desired, this can only be done for the adder output, on the Extra Modes tab.