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placement

spach

hi

can any one tell me how i can spread out std. cells placement evenly through out core area.  i have already used setplacemode -maxdensity option. tool is placing some modules cells and cells just beside macros  with density more than 90%.

 

regards,

sureshp

  • If the localized density is just in the vicinity of the hard macros and is causing pin access issues, it might be most effective to use a partial density screen in that region.  Here is an example of how you could add these and test the theory in a somewhat automated manner:

    #start with a floorplan that has hard macros preplaced
    #use addHaloToBlock to automate creation of placement halos around hard macro blocks
    #adjust the size to suit your situation
    addHaloToBlock 20 20 20 20 -allMacro

    #next,use a script in the gifts dir shipped with the software to convert those halos to hard blockages
    #so that we can convert them to partial density screens
    source <path_togift_scripts>/tcl/userBlockageUtils.tcl
    userConvertHalosToHardBlockages

    #finally, use a couple of dbSet calls to convert those to partial placement blockages
    dbSet top.fplan.pBlkgs.type partial
    dbSet top.fplan.pBlkgs.density 50

    If you're seeing general issues with localized placement density getting too high, there may be other things to try.  But if the problem is primarily along hard macros, I'd try this first.

    Please do let us know how this goes either way. I think this is a rather common situation so thanks for the question!

    Hope this helps,
    Bob

  • Hi Suresh, I am guessing that the design in general is low utilization. In this case, the placer tries to minimize wire length. This works great if you don't have congestion/timing issues. A classic symptom of that handling would be clumps of cells being placed. In this scenario, try: setPlaceMode -biasedPlace false Also, you can try to pad instances to make them look bigger. Good luck. Raja

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