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Altera_Forum's avatar
Altera_Forum
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14 years ago

How do I Force Quartus to generate Multiplier from ALMs?

I'm designing in a situation where I will have limited HW multipliers on a Stratix IV (they're being used for other things). I know that Quartus knows how to generate the most efficient fixed-point multiplier using only ALMs because it does it in things like the FIR Compiler II.

Is there an easy way to either generate a MegaFunction or use a code directive to have iQuartus do the best it can without using a hard-block?

Thanks!

/j

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    IIRC, if Quartus runs out of multipliers, it should start making ALM versions for you. But if you want to select which multipler will use logic, in VHDL you can use attributes: 

    
signal a, b : unsigned(8 downto 0); 
signal res : unsigned(17 downto 0); 
attribute multstyle : string; 
attribute multstyle of res : signal is "logic"; 
res <= a * b;
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    just FYI FIR Compiler II is quite smart and doing most of the heavy lifting with optimization, not Quartus. it's a very cool tool