Forcing Quartus to use Cyclone IV embedded multipliers

[Altera_Forum]

I really need to free up some LEs so it would really help if my LPM_MULT blocks could be implemented in the embedded multiplier blocks. How do I do that? 

 I've looked at the documentation and in Table 25 it suggests that setting DEDICATED_MULTIPLIER_CIRCUITRY to YES is the way forward, but where do I do that?

[Altera_Forum]

Hi Oliver, 

If you open the LPM_MULT block in the megawizard there is an implementation option where you can select "use dedicated multiplier circuitry".   CoGH

[Altera_Forum]

Yes, I found that, but all the options are greyed out.

[Altera_Forum]

Have you selected Cyclone IV in the megawizard? 

Otherwise you can edit the .vhd directly and set the DEDICATED_MULTIPLIER_CIRCUITRY parameter.

[Altera_Forum]

Yes, I've set the Cyclone IV in the megawizard. 

 I've looked in the .vhd file and it says   -- THIS IS A WIZARD-GENERATED FILE. DO NOT EDIT THIS FILE!  This doesn't surprise me, and I guess I can ignore it.  When you suggest setting DEDICATED_MULTIPLIER_CIRCUITRY, what's the syntax and where in the file does it belong?

[Altera_Forum]

It should already be there if it is a valid setting. 

I created an LPM_MULT for Cycline IV in Quartus 11.1 sp1 and that had the DEDICATED_MULTIPLIER_CIRCUITRY parameter in there but the implementation wasn't greyed either.

[Altera_Forum]

Could you please post up your VHDL? I'd like to try editing my file to see if that works. 

 Thanks in advance.

[Altera_Forum]

Here you are.

[Altera_Forum]

Thanks, that's very interesting. I'll see what happens.

[Altera_Forum]

Oliver, which device are you targeting? the CIVGX15 does not have hard multipliers

[Altera_Forum]

My device is an EP4CGX22

[Altera_Forum]

Editing the vhdl to add the hint didn't make any difference at all :(

[Altera_Forum]

Which version of Quartus are you using?

[Altera_Forum]

11.1 Web edition

[Altera_Forum]

I've learnt that Quartus does something different when you use an lpm_mult to square a number. It works for me when multipying by a constant!