Compairing RC value {Synthesis & Layout}

[jyothia]

Hi,

We are using a wire load model at the Synthesis stage {2k_6LM}, but after final layout we have different RC value. We need to compare the two RC value one during synthesis and one after extraction at final layout stage. Can you please help me how to proceed about this.
What sequence of command should I use{PrimeTime/Magma} .

 

[rca]

if you have two spef files, you can used osctrich tool.
With this tool, you can also determine the best RC factor to apply to PR tool and have a better match between PR & Primetime

 

[jyothia]

Can you tell me the procedure how we can execute it..any website

 

[rca]

osctrich is a simple graphic tool.
you need to load the spef from different tool and different corner. we can say
a-File>Import>SPEF
1-you load best & typical & worst spef generate from your PR (take care some place and route have different level of extractor, some simple to reduce the time processing, some for SI, need more time, but for SI fixing after PR is better to run a step of SI fixing violations)
2-you load best & typical & worst spef from signoff extractor
b-Correlate>Build Plot
you select one spef load for golden & one for target
c-Correlate>Draw Plot
will display the graph with the spef loaded and you can change the rc factor (left side) and recalculate...

 

[jyothia]

Thanks for your i/p. But the concern now is how I can generate a spef after synthesis. Is there a way..if so plz let me know.

Thanks once again for the help.

 

[rca]

to be able to generate a RC file (SPEF), you must have a routing or prerouting.

I don't know if synthesis tool can generate a spef, but it will not be very accurate without any routing.