What utilization do you target at the start? Considering a design with 70% vs 50% utilization, which would you take?

 o   Target Utilization at Start: The initial target core utilization for PnR typically ranges from 50% to 70%.

o    Lower utilization (e.g., 50-60%) provides more whitespace, making routing easier, reducing congestion, potentially improving timing (less detour), and offering more flexibility for CTS and ECOs. This is often preferred for high-performance designs or designs with known congestion challenges.

o    Higher utilization (e.g., 65-70%, sometimes even higher for specific blocks) aims to minimize die area (cost). However, it increases the risk of congestion, may make timing closure harder, and leaves less room for post-route optimizations and ECOs.

o   70% vs 50%: The choice depends heavily on design goals and characteristics:

o    Choose 50% if:

§  High performance/frequency is the primary goal.

§  The design has complex routing or known congestion hotspots.

§  Significant CTS overhead or late-stage ECOs are anticipated.

§  Power density / thermal concerns require spreading cells out.

§  Using an advanced node with restrictive routing rules.

o    Choose 70% if:

§  Area/cost minimization is the primary goal.

§  The design is relatively simple with moderate performance targets.

§  Congestion is not expected to be a major issue.

§  Minimal ECOs are expected.