Path-by-Path Clock Tree Uncertainty for Placeopt Optimization
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Solution Overview
Problem
Current placement and optimization techniques for semiconductor devices rely on a global uncertainty value that is not well-matched to actual clock tree variations, leading to overly pessimistic optimization decisions and potential design failures due to inadequate timing requirements.
Innovation Solution
The approach involves generating and utilizing multiple uncertainty values for an early clock tree to guide optimization and placement of circuit elements on a path-by-path basis, allowing for more accurate timing requirements and design goals to be met by propagating uncertainty values along clock and data paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a global uncertainty value is used to guide placement and optimization, then the process is simplified and can be applied uniformly across the entire design, but the timing constraints become overly pessimistic and do not accurately reflect actual clock tree variations at different points
Solution Approach 1:
The patent segments the global uncertainty value into multiple local uncertainty values associated with different regions or endpoints of the clock tree. Each local uncertainty value reflects the actual variation characteristics at its specific location, enabling path-by-path optimization with accurate timing constraints while maintaining computational tractability through localized analysis.
Solution Approach 2:
The patent applies local quality by assigning different uncertainty values to different regions of the clock tree based on their specific characteristics (depth, number of elements, signal traversal length). This allows each region to be optimized with its own appropriate uncertainty parameter rather than forcing a uniform global value, improving timing accuracy without excessive complexity.
2Reliability
If the global uncertainty value is increased to account for worst-case scenarios, then timing constraints become more conservative and may prevent design failures, but optimization decisions become overly pessimistic and may require unnecessary layout changes or gate size increases
Solution Approach 1:
The patent changes the uncertainty parameter from a single global value to multiple local values that better represent actual variations. This allows timing constraints to be set appropriately for each path without excessive conservatism, reducing unnecessary design iterations while maintaining reliability through accurate local uncertainty characterization.
3Measurement precision
If path-by-path optimization is performed with multiple uncertainty values, then timing constraint accuracy is improved and pessimism is reduced, but the computational complexity and processing time increase
Solution Approach 1:
By segmenting the clock tree into regions with local uncertainty values, the patent enables parallel or sequential processing of smaller path segments rather than analyzing the entire clock tree globally. This reduces computational complexity while maintaining timing accuracy through localized uncertainty-based optimization.
Data Source
AI summary
An approach is described for a method, system, and product, that includes identification/generation of a synthesized netlist for use in optimization and placement, generation and utilization of multiple uncertainty values for an early clock tree for guiding optimization and placed of circuit elements in a placeopt process that operates on a path by path basis. In some embodiments, the approach further comprises execution of clock tree synthesis, and routing the synthesized clock tree. In some embodiments, uncertainty values are propagated along data paths where each data path is associated with an uncertainty value, and where each path is optimized and placed on a path my path basis in order to meeting timing requirements and one or more design goals.