Placement and routing failures

The build stops in the floorplan, placement or routing phase.

Engineer 1 min read · Updated 2026-10-05

        On this page
        By phaseLet the lab offer a dieEnlarging the die yourselfThe die is far too bigThe build timed outAsk a specialistWhat not to do
      

The build card names the phase and the step that failed. Nearly all failures here have one cause: not enough room.

By phase#

Fails in	Usual cause	What to do
Floorplan	The die is too small for the design or for the power grid	A larger `DIE_AREA`
Placement	More cells than fit in the rows at the target density	A larger die
Routing, with congestion	Too many wires for the area	A larger die, or a lower `PL_TARGET_DENSITY_PCT`
Routing, with a few violations left	The router ran out of room in one crowded region	A somewhat larger die

Let the lab offer a die#

When a failed build reports that the design does not fit, the lab can offer a larger die. It is applied only if you accept it. Then run the build again.

Enlarging the die yourself#

DIE_AREA is four numbers in micrometres: left, bottom, right, top.

json

"DIE_AREA": [0, 0, 300, 300],

Area grows with the square: 300 by 300 is nine times 100 by 100. Grow in steps and build each time.

The die is far too big#

A build succeeds with a small block of cells in a mostly empty die. Nothing is wrong, and the area is wasted. Shrink the die and build again.

The build timed out#

A build may run for 60 minutes. A design too large for that is too large for the lab's limits today. Before deciding that, read the card: the layout may be finished and only a final check cut short, in which case running the build again often completes.

Ask a specialist#

After a build, these read its measured results:

nelix ai area
nelix ai routing

What not to do#

Do not edit the files under openlane/runs/. They are the build's working files. Change the design or the settings, and build again.

PlacementGiving every cell a position, and why where cells sit decides how fast the chip is.
RoutingDrawing the metal wires that join the cells, on several layers, without breaking a rule.

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