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Physical / electrical concepts

Net ordering

Which connection gets routed first. In sequential routing, early nets grab the best space and block later ones.

How it looks

Drawing: a routing grid, not a part of CORE3588
partpartAABB
A drawing on a routing grid. Routed in the order B then A, both nets fit (5 + 11 steps). In the order A then B, net B cannot be routed at all.

How it works

partpartB is boxed in: its only way out is the gap A tookAABBtwo nets, A (amber) and B (white). One gap each side of the right-hand partorder 1: A first. A takes the nearest gap: 9 stepsorder 2: B first. B goes straight up: 5 stepsthen A uses the far gap: 11 steps. Both done

Where it fits

Ordering rules of thumb: hardest or most constrained nets first (pairs, power, nets with few options). When no order works, routers use rip-up and reroute or negotiated congestion, which removes the dependence on order.

Ordering is part of dial 2, Negotiating, in the three dials and negotiation (routing).

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