Flip-Flop Placement for Regular Clock Tree Variation
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Solution Overview
Problem
Conventional VLSI logic cell placement mechanisms fail to prioritize flip-flops and synchronous logic cells, leading to irregular clock tree designs and increased clock on-chip variation, timing problems, and power consumption in circuits.
Innovation Solution
The proposed mechanism prioritizes the placement of flip-flops and synchronous logic cells based on clock gating, connectivity, and logic depth, allowing for the formation of more regular clock trees by analyzing the unplaced netlist and using graph clustering to predict clock tree and timing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cell placement mechanisms evaluate all logic cells simultaneously without prioritizing synchronous logic cells, then the placement process is simple and fast, but the clock tree design becomes irregular resulting in higher clock on-chip variation
Solution Approach 1:
The patent applies preliminary action by performing clock tree synthesis and placing synchronous logic cells (flip-flops) before placing asynchronous logic cells. This preliminary placement of synchronous cells based on clock tree requirements enables regular clock tree patterns and reduces clock on-chip variation, while the placement mechanism remains manageable through staged processing
2Reliability
If flip-flops are not placed with higher priority than asynchronous logic cells, then the placement process is straightforward, but timing problems and power consumption increase due to irregular clock tree designs
Solution Approach 1:
The patent implements preliminary action by completing clock tree synthesis and prioritizing synchronous logic cell placement before asynchronous logic cell placement. This ensures timing-critical elements are positioned to achieve regular clock tree designs, improving timing performance and reducing power consumption while maintaining a straightforward staged placement process
3Stability of the object's composition
If synchronous logic cells are placed in a regular pattern through prioritized placement, then clock tree regularity improves reducing clock on-chip variation, but the placement algorithm becomes more complex
Solution Approach 1:
The patent applies preliminary action by performing clock tree synthesis first to determine optimal synchronous logic cell positions, then placing these cells in regular patterns before asynchronous cell placement. This preliminary structuring achieves regular clock tree composition and reduced clock on-chip variation while keeping the overall algorithm manageable through sequential processing stages
Data Source
AI summary
Mechanisms to place flip-flops and other synchronous logic cells in a circuit layout in a clock on-chip variation-aware, predetermined order based on analysis of the clock gating, connectivity, and logic depth of the unplaced netlist. The resulting placements enable clock trees having a regular structure leading to improvements in clock on-chip variation, timing, and clock power.