Running the checks

Hint: Ask which checks need the foundry's rule deck, and which the design tools can do alone.

Geometry and connectivity come from the runsets; antennas do not. Extraction needs the foundry's own encoding of the rules, which is what a runset is. OpenROAD checks antennas from the routed database and the technology file, so that one can be run and repaired inside the flow. the open rule decks reference

Hint: Ask what a single number can and cannot tell you about a rule run.

Per rule, per run. A count is how progress is tracked, but it hides what matters: one violation can be a systematic problem repeated in a cell, and another can be a single stray shape. The flow writes the report so the results can be opened in the viewer. the open rule decks reference

Hint: Ask who has the authority to accept a violation, and on what basis.

Some rules are conservative or are met by construction in a macro the foundry supplied. Those cases are agreed and documented rather than fixed. A waiver is a decision with a name attached to it, not a way of silencing a checker. the open rule decks reference

Hint: Ask what has to be true at once, and whether timing alone is enough.

The checks constrain each other: fixing antennas adds diodes, fixing density adds fill that changes parasitics, and fixing timing moves cells. They must all hold on the same database, which is why sign-off is a gate on one final version rather than a series of independent passes. the open rule decks reference

Hint: Ask why passing at the typical condition is not enough.

Setup is usually worst slow and hot, hold worst fast and cold, and voltage drop worst when the supply is low and activity high. A part sold over a temperature and voltage range must meet all of them, which is what multi-corner analysis is for. Geometry is indeed corner-free. the open rule decks reference

Hint: Ask what has to be repeated after any change to the database.

Adding a buffer moves cells, which moves wires, which changes parasitics, density, and possibly antenna ratios. This coupling is why late changes are made as small, local edits and why a full sign-off run is expensive enough to be scheduled rather than casual. the open rule decks reference

Hint: Ask which check needs the most complete database.

The geometric and connectivity checks need everything: fill, the macros' real layouts, the seal ring. They therefore run on the merged layout at the end, while timing and electrical checks run repeatedly through the flow on the design database. the open rule decks reference

Hint: Ask what a clean result actually proves, and what it does not.

A deck has a version, a set of enabled rule groups, and often waivers. Running an old deck, or one missing the metal stack in use, gives a clean result that means little. This is why sign-off records which deck version was run, not only that it passed. the open rule decks reference

Hint: A full chip flat is enormous. Ask what can be checked only once.

A block used many times is verified once, and assembly checks the boundaries, the routing over the blocks, and the space between them. What this can miss is an interaction between a block's internals and something routed over it, so a final flat run is usually still done. the open rule decks reference

Hint: The rules are a document with a version, like anything else.

A revision can loosen a rule, tighten one, or replace it with a differently shaped one. Sign-off therefore records the exact deck version alongside the result, and a change of revision means running everything again. the open rule decks reference