I've got every time a difference result when I ran placedesign (related to congestion) after I've changed some power grid even though the same placementguides have been used. My question is how can I specify the startpoint (sheetfactor ??? ) so that the placedesign should start at the same point.Thanks.
Hi DN .
As we know that several factors will involved which cause difference in results.
BTW I dent get your changing topics on power grid ??
There are some default options which play a very imported role during placement and preplacement optimization.
I think that you are have explicitly specified (noTimingDriven) option in setPlaceMode.
Are you expecting default RC factor setting , if YES then below is the method to set it.
##### Set RC Factor #####
setRCFactor -defcap 1.000 -detcap 1.000 -res 1.000
FYI . suggestions from manual :
_ The following commands perform non-timing-driven placement:
_ The following commands disable scan chain reordering:
_ The following command disables the pre-placed buffer tree removal:
_ The following command enables the in-place optimization flow:
_ After the design is placed, the following command performs incremental placement, and
disables the pre-placed buffer tree removal:
Let me know if you need anything more.
Let me add few more comments on "placedesign" command :
Based on your explanation not only RC extraction tunes placement but also timing analysis, trail routing and placement option settings.
So you also need to set
setPrerouteAsObs ( example for placement obstructions)
setPlaceMode ( you can specify max touting layer )
Trial Route Option (you need to specify same for every trail).
Let me know how your trail route congestion report was every time you run.
Thanks for your quickly reponses!I know that several factor will involve that cause diffrence in result but I'm using the same options, same guides, same netlist,... from the previous run.And it looks like the congestion is changing every time because some modulesare placed in an another areas. The result has not much impact for the timing in generally. But for a high frequent design when a little bit change of congestions can harm the timing clean on some critical paths.For more details what I've used:- cadence_fe 04.20-s315_1_USR2- Hierarchy netlist- Timingdriven- nopreplaceopt- noreordescanRegards,
Hi ,I seems that you agreed that you have changed the placement of modules or fp. causing the same, As you know that trail route choose different paths when module placement change.suggesion : try with "-incremental" option.Yes I too agree that global congestion effects every design . see the cause and avoid it by placing density screen .
Hi ,I seems that you agreed that you have changed the placement of modules or fp. causing the same, As you know that trail route choose different paths when module placement change.suggesion : try with "-incremental" option.Yes I too agree that global congestion effects every design . see the cause and avoid it by placing density screen .Thanks , Non -AE
Hi I got you point what you mean in your mail,I suggest you to add "Fence" option in your design instead of guide-OK(The module is a hard constraint in the core design area.)Note: Fence groups can potentially cause overlaps that cannot be corrected becausethe Encounter software cannot move the cells out of the group. So take care of each effective module target utilization (TU=%) value to represent their physical design .Not an AE .