o H-Tree:
Advantages:
Zero Skew (Ideal): Theoretically capable of achieving zero skew if sinks are perfectly distributed and the tree is perfectly balanced.
Symmetric Structure: Predictable and regular routing pattern.
Disadvantages:
Impractical for Real Designs: Assumes uniform sink distribution, which rarely occurs. Blockages and routing obstacles disrupt the ideal structure.
High Insertion Delay: Can lead to long paths from the root to sinks.
Resource Intensive: Can consume significant routing area, especially on preferred layers.
Large Central Driver: Often requires a very large buffer at the root, consuming significant power and area.
Less Flexible: Rigid structure makes it hard to adapt to local density variations or timing requirements.
Advantage of Using Both Buffers and Inverters:
Flexibility: Provides the CTS tool with more options for delay balancing and phase control.
Finer Delay Tuning: Inverters typically have slightly lower delay than equivalent-drive buffers (since a buffer is ~2 inverters). Using inverters allows for finer granularity in delay insertion.
Area/Power Optimization: A pair of inverters might consume less area/power than a single equivalent buffer. The tool can choose the most efficient option based on availability and design constraints.