Steiner tree based rotary clock routing with bounded skew and capacitive load balancing

A novel rotary clock network routing method is proposed for the low-power resonant rotary clocking technology which guarantees: 1. The balanced capacitive load driven by each of the tapping points on the rotary rings, 2. Customized bounded clock skew among all the registers on chip, 3. A sub-optimally minimized total wirelength of the clock wire routes. In the proposed method, a forest of steiner trees is first created which connects the registers so as to achieve zero skew and greedily balance the total capacitance of each tree. Then, a balanced assignment of the steiner trees to the tapping points is performed to guarantee a balanced capacitive load on the rotary network. The proposed routing method is tested with the ISPD clock network contest and IBM r1-r5 benchmarks. The experimental results show that the capacitive load imbalance is very limited. The total wirelength is reduced by 64.2% compared to the best previous work known in literature through the combination of steiner tree routing and the assignment of trees to the tapping points. The average clock skew simulated using HSPICE is only 8.8ps when the bounded skew target is set to 10.0ps.