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  #1 (permalink)  
Old 05-24-2006, 07:15 PM
Nial Stewart
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Default Stopping Quartus using multipliers?

I'm prototyping a design on an Altera NIOS evaluation board with
an EP2C35. The design will eventually be targeted at a much smaller
device, possibly an EP2C5.

I have a couple of FIR filters that I want implemented in the FPGA
fabric rather than in the dedicated multipliers so I can guage the
footprint/performance. Quartus keeps using the multipliers and
I can't work out how to stop it.

Can anyone help?



Nial



----------------------------------------------------------
Nial Stewart Developments Ltd Tel: +44 131 561 6291
42/2 Hardengreen Business Park Fax: +44 131 561 6327
Dalkeith, Midlothian
EH22 3NU
www.nialstewartdevelopments.co.uk




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  #2 (permalink)  
Old 05-24-2006, 07:40 PM
Mike Treseler
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Default Re: Stopping Quartus using multipliers?

Nial Stewart wrote:

> I have a couple of FIR filters that I want implemented in the FPGA
> fabric rather than in the dedicated multipliers so I can guage the
> footprint/performance. Quartus keeps using the multipliers and
> I can't work out how to stop it.


Could you code something that uses up all the multipliers?

-- Mike Treseler
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  #3 (permalink)  
Old 05-24-2006, 09:31 PM
Slurp
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Default Re: Stopping Quartus using multipliers?


"Nial Stewart" <[email protected]> wrote in message
news:[email protected]
> I'm prototyping a design on an Altera NIOS evaluation board with
> an EP2C35. The design will eventually be targeted at a much smaller
> device, possibly an EP2C5.
>
> I have a couple of FIR filters that I want implemented in the FPGA
> fabric rather than in the dedicated multipliers so I can guage the
> footprint/performance. Quartus keeps using the multipliers and
> I can't work out how to stop it.
>
> Can anyone help?


In the multiplier megafunction (LPM_MULT) on page 2 there are switches
available to turn off the use of the chips dedicated multipliers and use
logic elements instead.

Slurp


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  #4 (permalink)  
Old 05-24-2006, 09:46 PM
Nial Stewart
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Default Re: Stopping Quartus using multipliers?

"Slurp" <[email protected]> wrote in message
news:[email protected]

> In the multiplier megafunction (LPM_MULT) on page 2 there are switches available to turn off the
> use of the chips dedicated multipliers and use logic elements instead.
> Slurp



I'm inferring the multipliers so don't have this control unfortunately.



Nial


----------------------------------------------------------
Nial Stewart Developments Ltd Tel: +44 131 561 6291
42/2 Hardengreen Business Park Fax: +44 131 561 6327
Dalkeith, Midlothian
EH22 3NU
www.nialstewartdevelopments.co.uk


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  #5 (permalink)  
Old 05-24-2006, 09:48 PM
Nial Stewart
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Default Re: Stopping Quartus using multipliers?

"Mike Treseler" <[email protected]> wrote in message news:[email protected]
> Nial Stewart wrote:
>> I have a couple of FIR filters that I want implemented in the FPGA
>> fabric rather than in the dedicated multipliers so I can guage the
>> footprint/performance. Quartus keeps using the multipliers and
>> I can't work out how to stop it.

>
> Could you code something that uses up all the multipliers?
> -- Mike Treseler



I suppose I could Mike, but it's a lot of hassle for what will hopefully
just be a switch/constraint.


Nial.



----------------------------------------------------------
Nial Stewart Developments Ltd Tel: +44 131 561 6291
42/2 Hardengreen Business Park Fax: +44 131 561 6327
Dalkeith, Midlothian
EH22 3NU
www.nialstewartdevelopments.co.uk


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  #6 (permalink)  
Old 05-24-2006, 10:03 PM
Henry Wong
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Default Re: Stopping Quartus using multipliers?

> Quartus keeps using the multipliers and
> I can't work out how to stop it.
>



How about setting

Analysis and Synthesis settings
-> More Settings
-> Maximum DSP Block Usage

to 0? (Default -1)
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  #7 (permalink)  
Old 05-24-2006, 10:17 PM
Nial Stewart
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Default Re: Stopping Quartus using multipliers?

"Henry Wong" <[email protected]> wrote in message
news:[email protected] ...
>> Quartus keeps using the multipliers and
>> I can't work out how to stop it.

> How about setting
>
> Analysis and Synthesis settings
> -> More Settings
> -> Maximum DSP Block Usage
>
> to 0? (Default -1)



Thanks Henry, that did it.

I mistakenly presumed that -1 was a lower number than 0 and so
changing this to 0 wouldn't have made any difference.

Intuitive isn't it :-)


Nial


----------------------------------------------------------
Nial Stewart Developments Ltd Tel: +44 131 561 6291
42/2 Hardengreen Business Park Fax: +44 131 561 6327
Dalkeith, Midlothian
EH22 3NU
www.nialstewartdevelopments.co.uk


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  #8 (permalink)  
Old 05-24-2006, 10:27 PM
KJ
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Default Re: Stopping Quartus using multipliers?

> I mistakenly presumed that -1 was a lower number than 0 and so
> changing this to 0 wouldn't have made any difference.


Must've been an unsigned -1 which would make it > 0

KJ

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