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Adventurer
Adventurer
5,088 Views
Registered: ‎05-24-2013

ISE 14.7 Placer cost table Understanding

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Hello,

 

I have a question to understand the ISE 14.7 Placer cost tables. I have LOC ed my DSP s and BRAM s and I get 775 Setup errors. Now I am running the SmartXplorer in the "iterate Cost Table only" mode, where it just iterates through 1-100 as starting placer cost table. I have read the AR35534 and if I understood correctly, 1 is a random starting placement and 7 is another random starting placement. But does this placement completely overthrow my manually placed DSPs and BRAMs and picks up a totally random placement? Or does it take my fixed instances into account and goes for a random initial placement for the rest of the logic?

 

Thanks

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Moderator
Moderator
9,554 Views
Registered: ‎01-16-2013

Re: ISE 14.7 Placer cost table Understanding

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@conanind,

 

The tool will always consider the user constraints unless there is syntax error.

So yes, the tool will consider you location constraints into account. You can verify them by opening the post routed ncd in FPGA_EDITOR.

 

--Syed

 

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Kindly note- Please mark the Answer as "Accept as solution" if information provided is helpful.
Give Kudos to a post which you think is helpful and reply oriented.

Did you check our new quick reference timing closure guide (UG1292)?
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Moderator
Moderator
9,555 Views
Registered: ‎01-16-2013

Re: ISE 14.7 Placer cost table Understanding

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@conanind,

 

The tool will always consider the user constraints unless there is syntax error.

So yes, the tool will consider you location constraints into account. You can verify them by opening the post routed ncd in FPGA_EDITOR.

 

--Syed

 

---------------------------------------------------------------------------------------------
Kindly note- Please mark the Answer as "Accept as solution" if information provided is helpful.
Give Kudos to a post which you think is helpful and reply oriented.

Did you check our new quick reference timing closure guide (UG1292)?
---------------------------------------------------------------------------------------------
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Adventurer
Adventurer
5,081 Views
Registered: ‎05-24-2013

Re: ISE 14.7 Placer cost table Understanding

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Thank you.

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Adventurer
Adventurer
5,040 Views
Registered: ‎05-24-2013

Re: ISE 14.7 Placer cost table Understanding

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I got some interesting results running the design with various Starting placer cost tables.

 

costTables.PNG

I must admit I am regretting that I was not aware of this tool earlier, since it has produced some excellent results for me. I did not download the bitstream to FPGA yet so I do not know if other parts of my design got screwed but that should not be the case.

 

Anyway the results are good but I am suprised to see that they are so different. I can't understand the reason behind this. In the AR# 35534, it says that a cost table is a "random seed of placement". I guess there are worlds in between start cost tables "9" and "10" since one had timing closure and the other 31255 setup errors.

 

 

 

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