A Parameterized Timing‐aware Flip‐flop Merging Algorithm for Clock Power Reduction
Chaochao Feng1,a, Daheng Yue1,b, Zhenyu Zhao1,c and Zhuofan Liao2
1National University of Defense Technology, Changsha, China
afengchaochao@nudt.edu.cn
byuedaheng@nudt.edu.cn
czyzhao@nudt.edu.cn
2Changsha University of Science & Technology, China
csulzf@gmail.com
ABSTRACT
In modern integrated circuits, the clock power contributes a dominant part of the chip power. Clock power can be reduced effectively by utilizing multi‐bit flip‐flops. In this paper, a parameterized timing‐aware flip‐flop merging algorithm is proposed for clock power reduction. The single‐bit flip‐flops are merged into multi‐bit flip‐flops after placement & optimization and before clock network synthesis with consideration of function information, scan chain information, distance and timing constraints. The algorithm can be configured with different parameters, such as the bit‐number of MBFF, the setup timing margin and the distance margin. Experimental results under an industrial design show that compared with the basic design without MBFF, the design with 2‐bit, 4‐bit, 6‐bit, and 8‐bit MBFFs can save 7.5%, 12%, 11.8% and 11.1% total power consumption respectively. Using MBFF4 to replace 1‐bit FFs is the best choice for the design optimization, which achieves minimum area and total power consumption. We also compare the designs with MBFF4 replacement under five different setup timing margins and distance margins. Without violating any timing constraint, it is better to set the setup timing margin as small as possible to achieve best power optimization. The distance margin (100µm, 30µm) is the best choice for this industry design to achieve minimum power consumption.
