Register clustering (clock-aware)

Clock-aware placement: register clustering. The teal cells are registers (flip-flops) that all share one clock. If they are scattered, the clock tree that reaches every one of them is long and burns power. So group them.

• Registers clustered - keep all the registers inside one tight box (the dashed clock-group outline). Its span - width plus height - must stay under the limit, so the clock tree stays short.
• Wirelength under target - each register also drives a data cell that must reach its boundary pin, which pulls the registers apart. Keep total wire under target anyway.

Pack the registers together for the clock while still letting the data reach its pins, then Submit design.