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timing driven and congestion driven

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Full Member level 3
Jun 2, 2007
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How will u know whether to do a Timing Driven placement or Congestion Driven placement?

timing driven placement :
after the 1st round of placement, the timing tool ( PT) has 2 be provided with the placed netlist and the constraints.
the PT now gives a output file .sdf which contains the delay info wrt to the paths, now this .sdf can be read into ur placement tool along with the initial placed netlist to obtain a "timing driven placement" of ur design

I m not sure wrt the "congestion driven placement"



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timing driven placement is the cell in a timing critical path are placed close to gether to reduced routeing related delays .it is maintance the timing

congestion driven is the occurs if there are one or more wire to be routed than available is didnt maintance of timing


anyone can explain more on "congestion placement"?

Hey vamshi can u explain me clearly about congestion driven placement ?? i didn't get ur point wts tht?last sentence

Added after 11 minutes:

Hey Darylz

I don't think that there is a word like placement congestion
Bcz congestion comes only after routing where it shows that how many metallayers are required and how many are available for the routing................

Correct me if i am wrong...

Bye take care

timing driven placement is done when we are dealing with timing critical designs. here the placement of std cells will be done in such a way that the cells belonging to a critical path( paths which have max negative slack) will be placed close together. but here, the congestion might be more( especially after routing).

congestion driven placement is chosen in those designs where the die size is small. hence, the seperation between std cells will be increased to take in to account the routing that will be done in the later stage. but the timing wil be afftected to an extend since the seperation between the cells increases.

hope this helps! :D

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