Due to a problem in the Quartus® II software, you may see this warning when using certain Altera® DSP megafunctions or DSP Builder cores and targeting Stratix® III or Stratix IV devices. These functions always target dedicated multiplier circuitry by default and DSP block balancing cannot retarget these functions to logic implementations.
To work around this problem and manually retarget a function to use logic instead of dedicated multiplier circuitry, add the following assignments for each instance you want to retarget to your project's Quartus II Settings File (.qsf):
set_parameter -name dedicated_multiplier_circuitry NO -to <instance_path>
set_parameter -name dsp_block_balancing "Logic Elements" –to <instance_path>
This problem is scheduled to be fixed in a future release of the Quartus II software.