I'm attempting to harden my design using option 1 in the caravel/openlane readme from the develop branch. I started out by copying the

user_proj_example/config.tcl

and modifying it appropriately. I then commented out

set ::env(DIE_AREA)

setting of

0 0 600 600

since that is fairly small (and the design needs more room). When I do this, the core area remains very small and modifying

set ::env(PL_TARGET_DENSITY

has no effect. Of course this then results in a RePlAce error saying

Filler area is negative!! Please put higher target density or Re-floorplan to have enough coreArea

. If I uncomment

set ::env(DIE_AREA)

and adjust manually, I get past the core area issues. So my questions are, 1.) where is the default core area parameter being set when

DIE_AREA

setting is commented out in the config.tcl? 2.) For this option (option 1) of hardening our design, is setting

DIE_AREA

to specific values required?

Density is not the area used. Try

FP_CORE_UTIL

Thanks for the reply. I've commented out

FP_SIZING

and

DIE_AREA

and added

FP_CORE_UTIL

. However, the utilization % (as reported in

replace.log

) is always 1% greater than the value I set for

FP_CORE_UTIL

. Again, if I change

DIE_AREA

from

0 0 600 600

to

0 0 1250 1250

, the RePlAce step succeeds. I'm trying to understand the correlation between

FP_CORE_UTIL

and the default core area used when

DIE_AREA

is not specified.

My understanding is that it'll just take the estimated gate are after synthesis and try to make that area

X

percent of the total area. Of course this is just an estimate at that point and so by the time you get to placement, there will be small differences.

Ok, I'll continue to manually specify

DIE_AREA

as that gets me past this issue.