PLE - physical layout estimator

Hi Eng,

By GPS I meant, Only Placing the data and Not the routing part.

You are correct that RC factors should be calculated with QX spef but that is to corelate before and after route.

My question was, That I have a database which is timing clean in RTL compiler (Cadence Logical synthesis tool) but has violations when I place it using GPS(Cadence encounter), so can I use some RC scaling factors in Rtl compiler PLE flow so as to correlate my Timing results before placement and after placement.

Regards,
Vikas

Hi Vikas,

in the past we've had reasonable success using the path_adjust flow. In my mind, this is a better approach since, unless you truly have a global scaling problem, you will penalize all paths in the design to address only a handful that have correlation issues. Moreover, the path_adjust flow will gain you back some on the correlation issues where things are pessimistic in synthesis.

just my 2c.
gh-

Vikas,

     The way you deal with correlation between RC's PLE results and the physical timing really depends on the cause of the differences. Scale factors may be the right answer if there is a large difference between the lef/capTable data and the final QX numbers. This would be the case if you saw that statistically all the nets in the design were off by some percentage. It is also possible that the correlation may be due to some very long nets that are harder to predict during synthesis. These can be addressed in a number of different ways. You may want to use a path_adjust flow for these nets, or in some cases allow FE to fix them later. These would have to be dealt with on a case by case basis. I would strongly recommend that you spend some time understanding the root cause of these violations in order to devise a strategy to address them.

Hope this helps.

jflieder