Causes for large -ve slack during pre-place STA

[useless_skew]

If there is a huge -ve slack during pre-placement STA, what is the reason for that?
According to me, it is due to a poorly synthesized netlist or due to some constraints in the timing constraints file.

Is there any other reason for this large -ve slack?

Does the floorplan/macro placement affect pre-placement timing analysis results in any way?

Thanks.

 

[pranam.bhagavan]

If there is a huge -ve slack during pre-placement STA, what is the reason for that?
According to me, it is due to a poorly synthesized netlist or due to some constraints in the timing constraints file.

Is there any other reason for this large -ve slack?

Does the floorplan/macro placement affect pre-placement timing analysis results in any way?

Thanks.

Yes, it may due to that not constrainted during synthesis or over constrained or it may be real violation which cant met.

Floorplan and macro placement will make timing worse, not better as synthesis assumes ideal net delay.

 

[vlsitechnology]

The very good reason is..The tool will add buffers in unwanted locations so that is the reason most of the people will not go for Preplacement timing analysis..But they will go for Inplacement Optimization....We also had the same situation but later on we came to know

Reply me if u have any doubts..
And don't forget to push help button
Bye take care