TIMBER: A Fast Algorithm for Timing and Power Optimization Using Multi-bit Flip-flops

Multi-bit flip-flop (MBFF) banking and debanking is a widely adopted technique for optimizing power and total negative slack (TNS) during the post-placement stage of digital design. While banking flipflops can reduce both power and area, excessive banking may lead to increased TNS due to significant register displacement, as well as bin density violations (BDVs) caused by over-placing MBFFs in legalized regions. To address these challenges, the EDA community recently organized a CAD Contest seeking innovative solutions from both academia and industry. In response, we present TIMBER, a fast and effective optimization algorithm that balances competing objectives in MBFF placement. Unlike existing methods, TIMBER employs a bin-density-aware placement strategy that simultaneously minimizes BDVs and TNS, while also achieving gains in power and area efficiency. To further enhance the runtime performance, TIMBER incorporates a parallelization strategy. Experimental results on the official 2024 CAD Contest benchmarks demonstrate that TIMBER outperforms the first-place winner, delivering on average $13.08 \times$ better solution quality, zero BDVs, $5.06 \times$ faster single-threaded runtime, $3.56 \times$ lower memory usage and up to $72.49 \times$ speedup in multi-threaded execution.