PhD graduated
Team : CIAN
Departure date : 09/30/2011

Supervision : Habib MEHREZ

Exploration and optimization of application specific heterogeneous tree-based fpga architectures.

Generalized and programmable nature of Field Programmable Gate Arrays (FPGAs) has made them a popular choice for the implementation of digital circuits. However, the programmability of FPGAs makes them larger, slower and more power consuming than their counterpart ASICs; hence making them unsuitable for applications requiring high density, performance and low power consumption. The main theme of this work is to improve the area of FPGAs. For this purpose, a detailed exploration and optimization of two FPGA architectures is performed: one is the well known mesh-based FPGA architecture while other is tree-based architecture that remains relatively unexplored despite its better performance and routing predictability. Further, a detailed comparison between the two architectures is also presented to highlight their respective advantages and disadvantages. The exploration and optimization of two architectures start with the introduction of heterogeneous hard-blocks in both architectures. In this work, first we present a new environment for exploration of heterogeneous tree-based FPGA architecture. This environment is flexible in nature and allows to explore different architecture techniques with varying types of hard-blocks. Further, in this work, we present an exploration environment for heterogeneous mesh-based FPGA architecture. The two environments are used to explore a number of techniques for both architectures. These techniques are later evaluated using different heterogeneous benchmarks that are placed and routed on the two architectures using a specifically developed software flow. A detailed comparison between different techniques of the two architectures is performed and results show that on average, tree-based architecture gives better overall results than mesh-based architecture. Generalized mesh and tree-based FPGA architectures are further improved by turning them into application specific FPGAs. An application specific inflexible FPGA (ASIF) is a modified FPGA with reduced flexibility and improved density. This work initially presents a new homogeneous tree-based ASIF and when compared to an equivalent tree-based FPGA, it gives 64% area gain. Further the comparison between equivalent mesh and tree-based ASIFs shows that tree-based ASIF gives 12% better area results than mesh-based ASIF. We also extend the ASIF to heterogeneous domain and experimental results show that, on average, heterogeneous tree-based ASIF gives 70% area gain when compared to equivalent heterogeneous tree-based FPGA. Further the comparison between heterogeneous mesh and tree-based ASIFs reveals that tree-based ASIF gives either equal or better results than mesh-based ASIF.

Defence : 07/12/2011

Jury members :

CHILLET Daniel , IRISA, Lannion,France. (Rapporteur)
FESQUET Laurent , TIMA, Grenoble, France. (Rapporteur)
ANCEAU Francois , LIP6, Paris, France. (Examinateur)
DANGER Jean-Luc, LTCI, Paris, France. (Examinateur)
GRANADO Bertrand , ETIS, Cergy-Pontoise, France. (Examinateur)
MEHREZ Habib , LIP6, Paris, France. (Directeur de Thèse)

Departure date : 09/30/2011

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