Implementation of High Speed Routing using Buffer Optimization

Abstract

Introduction: High-speed on-chip communication is critical in modern VLSI design to meet stringent performance requirements. As technology scales down and circuit complexity grows, interconnect delay has emerged as a dominant factor affecting overall chip performance. Efficient routing plays a key role in ensuring fast and reliable signal distribution across the chip’s metal layers. Among the techniques to enhance routing performance, buffer optimization stands out, this involves the strategic insertion and sizing of buffers along long interconnects to minimize delay, prevent signal degradation and balance load capacitance. Proper buffer placement not only improves signal integrity and timing but also mitigates challenges such as excessive loading, noise and power inefficiency

Objectives: To model different design cases by modifying design files to reflect various scenarios like input-register, register-register, register-output and input-output; To analyze critical timing paths between macros; To optimize the design to meet timing requirements; To perform timing-driven placement.

Methods: The project aims to improve the timing performance in VLSI systems by analyzing and optimizing key timing paths across different scenarios, including IP-to-boundary, register-to-register and standard cell connections, within both single and multi-clock domains. Various design cases are developed to reflect realistic System On Chip (SOC) architectures and static timing analysis is conducted to identify the most critical paths. Buffer insertion is then strategically optimized to reduce delays and enhance signal quality, with attention to placement and sizing to maintain efficiency in area and power usage. A timing-driven placement approach is implemented to ensure that high-priority nets are optimally positioned during layout. The overall workflow is compatible with the standard Register Transfer Level (RTL)-to-GDSII design flow, ensuring relevance and applicability in real-world chip design processes.

Results: A detailed analysis aimed to improve timing efficiency in VLSI systems by optimizing buffer insertion between macros, thereby enabling timing-driven placement. Multiple timing scenarios were examined, including interactions between fixed blocks and standard cells, as well as standard cell-to-cell and combinational logic paths. These case studies were used to model and analyze different signal transitions, such as input-to-register, register-to-register, register-to-output and direct input-to-output flows.

Conclusions: With the growing complexity of system-on-chip designs and the demand for faster on-chip communication, maintaining timing accuracy across long interconnect paths has become a significant concern. To address this, various timing scenarios were modeled including fixed block to standard cell, standard cell to standard cell and interface-based paths. The impact of buffer placement on timing performance was evaluated using detailed timing reports from different placement stages. The findings revealed notable improvements in slack, reduced HPWL and optimized routing conditions. Implementing these strategies within the OpenROAD design flow confirmed that buffer insertion effectively aids in timing closure, signal integrity and overall layout quality.