How Do I Know If My Signal Will Have Integrity Problems Before I Build the Board

Best practices and stack-up recommendations will get you close but they won't tell you whether your differential pairs actually pass at the data rate you're targeting. The only way to know before the board goes to fab is to simulate it. This video walks through the topology extraction and eye diagram workflow in Allegro X with Sigrity X Aurora, using a USB differential pair on a 12-layer AI PCB as the example. The result: confirmed USB 2.0 performance at 480Mbps, a clean eye at 1Gbps, and a fully collapsed eye at 5Gbps which tells you exactly where this layout's limit is before you commit to fabrication. Every trace segment, via transition, and layer change is included in the simulation. All of it matters.