Clock buffer insertion

Clock buffer insertion. The root cannot drive the whole clock tree at once: past a load limit, its transition (slew) degrades. Break the tree into regions with buffers by clicking the internal hubs.

• Every driver under the slew load - a buffer re-drives everything below it, splitting the load. Every driver (the root and each buffer) must drive a load under the limit, so too few buffers leaves a region overloaded.
• Buffers within budget - buffers cost power, and you have a budget. You cannot just buffer every hub: over-buffering busts the budget.

The catch is that where you buffer matters. A buffer high in the tree covers a big subtree but may still be overloaded; buffers lower down each cover less. Find a minimal set of hubs that puts every driver under the limit without exceeding the budget, then Submit design.