293 research outputs found
A Metaheuristic Method for Fast Multi-Deck Legalization
Department of Electrical EngineeringIn the field of circuit design, decreasing the transistor size is getting harder and harder. Hence, improving the circuit performance also becoming difficult. For the better circuit performance, various technologies are being tired and multi-deck standard cell technology is one of them. The standard cell methodology is a fundamental structure of EDA (Electric Design Automation). Using the standard cell library, EDA tools can easily design, and optimize the physical design of chips.
In order to conventional standard cell, multi-deck standard cell occupies multiple rows on the chip. This multiple occupation increases complexity of the circuit physical design for EDA tools. Thus, legalization problem has become more challenging for the multi-deck standard cells. Recently, various multi-deck legalization methods are proposed because the conventional single-deck legalization method is not effective for multi-deck legalization. A state-of-the-arts legalization method is based on quadratic programming with the linear complementary problem(LCP). However, these previous researches can only cover the double-deck case because of runtime burden.
In this thesis, we propose the fast and enhanced the multi-deck standard cell legalization algorithm which can handle higher than double-deck standard cell cases. The proposed legalization method achieves the most fastest runtime result for the dominant number of benchmarks on ICCAD Contest 2017 [1] compared with Top 3 results.ope
Custom Cell Placement Automation for Asynchronous VLSI
Asynchronous Very-Large-Scale-Integration (VLSI) integrated circuits have demonstrated many advantages over their synchronous counterparts, including low power consumption, elastic pipelining, robustness against manufacturing and temperature variations, etc. However, the lack of dedicated electronic design automation (EDA) tools, especially physical layout automation tools, largely limits the adoption of asynchronous circuits. Existing commercial placement tools are optimized for synchronous circuits, and require a standard cell library provided by semiconductor foundries to complete the physical design. The physical layouts of cells in this library have the same height to simplify the placement problem and the power distribution network. Although the standard cell methodology also works for asynchronous designs, the performance is inferior compared with counterparts designed using the full-custom design methodology. To tackle this challenge, we propose a gridded cell layout methodology for asynchronous circuits, in which the cell height and cell width can be any integer multiple of two grid values. The gridded cell approach combines the shape regularity of standard cells with the size flexibility of full-custom layouts. Therefore, this approach can achieve a better space utilization ratio and lower wire length for asynchronous designs. Experiments have shown that the gridded cell placement approach reduces area without impacting the routability. We have also used this placer to tape out a chip in a 65nm process technology, demonstrating that our placer generates design-rule clean results
Implementation and optimization of an integrated circuit placement algorithm in parallel environment
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Nanometer VLSI placement and optimization for multi-objective design closure
In a VLSI physical synthesis flow, placement directly defines the interconnection,
which affects many other design objectives, such as timing, power consumption,
congestion, and thermal issues. With the scaling of technology, the relative interconnect
delay increases dramatically. As a result, placement has become a bottleneck
in deep sub-micron physical synthesis. In this dissertation, I propose several
optimization algorithms from global placement, placement migration, timing driven
placements, to incremental power optimizations for multi-objective VLSI design
closure. The first work is DPlace, a new global placement algorithm that scales
well to the modern large-scale circuit placement problems. DPlace simulates the
natural diffusion process to spread cells smoothly over the placement region, and
uses both analytical and discrete techniques to improve the wire length. However,
global placement is never sufficient for multi-objective design closure, a variety of
design objectives have to be improved incrementally, such as timing, routing congestion,
signal integrity, and heat distribution. Placement migration is a critical step
to address the cell overlaps appearing during incremental optimizations. To achieve
high placement stability, I propose a computational geometry based placement migration
flow to cope with placement changes, and a new stability metric to measure
the “similarity” between two placements accurately. Our placement migration algorithm
has clear advantage over conventional legalization algorithms such that the
neighborhood characteristics of the original placement are preserved. For timing
closure in high performance designs, I present a linear programming based incremental
timing driven placement to improve the timing on critical paths directly.
I further present an efficient timing driven placement algorithm (Pyramids). Two
formulations of Pyramids are proposed, which are suitable for different optimization
stages in a physical synthesis flow. Both approaches find the optimal location
for timing of a cell in constant time, through computational geometry based approaches.
For fast convergence of design closure, placement should be integrated
with other optimization techniques. I propose to combine placement, gate sizing
and Vt swapping techniques to reduce the total power consumption, especially the
leakage power, which is becoming increasingly critical for nanometer VLSI design
closure.Electrical and Computer Engineerin
An Effective Routability-driven Placer for Mixed-size Circuit Designs
We propose a routability-driven analytical placer that aims at distributing pins evenly. This is accomplished by including a group of pin density constraints in its mathematical formulation. Moreover, for mixed-size circuits, we adopt a scaled smoothing method to cope with fixed macro blocks. As a result, we have fewer cells overlapping with fixed blocks after global placement, implying that the optimization of the global placement solution is more accurate and that the global placement solution resembles a legal solution more. Routing solutions obtained by a commercial router show that for most benchmark circuits, better routing results can be achieved on the placement results generated by our pin density oriented placer
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Improved Physical Design for Manufacturing Awareness and Advanced VLSI
Increasing challenges arise with each new semiconductor technology node, especially in advanced nodes, where the industry tries to extract every ounce of benefit as it approaches the limits of physics, through manufacturing-aware design technology co-optimization and design-based equivalent scaling. The increasing complexity of design and process technologies, and ever-more complex design rules, also become hurdles for academic researchers, separating academic researchers from the most up-to-date technical issues.This thesis presents innovative methodologies and optimizations to address the above challenges. There are three directions in this thesis: (i) manufacturing-aware design technology co-optimization; (ii) advanced node design-based equivalent scaling; and (iii) an open source academic detailed routing flow.To realize manufacturing-aware design technology co-optimization, this thesis presents two works: (i) a multi-row detailed placement optimization for neighbor diffusion effect mitigation between neighboring standard cells; and (ii) a post-routing optimization to generate 2D block mask layout for dummy segment removal in self-aligned multiple patterning.To achieve advanced node design-based equivalent scaling, this thesis presents two improved physical design methodologies: (i) a post-placement flop tray generation approach for clock power reduction; and (ii) a detailed placement approach to exploit inter-row M1 routing for congestion and wirelength reduction.To address the increasing gap between academia and industry, this thesis presents two works toward an open source academic detailed routing flow: (i) a complete, robust, scalable and design ruleaware dynamic programming-based pin access analysis framework; and (ii) TritonRoute – the open source detailed router that is capable of delivering DRC-clean detailed routing solutions in advanced nodes.This thesis concludes with a summary of its contributions and open directions for future research
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