VTR 9: Open-Source CAD for Fabric and Beyond FPGA Architecture Exploration

Abstract

VTR 9 represents a significant advancement in the open-source Verilog-to-Routing CAD flow, focusing on enabling comprehensive exploration of next-generation reconfigurable architectures. This release introduces powerful modeling capabilities for complex heterogeneous fabrics, moving beyond traditional FPGAs to support sophisticated system designs. The updated toolchain allows researchers to rigorously evaluate novel architectural trade-offs, improving the efficiency and scalability of future hardware designs.

Report

Key Highlights

• Major CAD Release: VTR 9 is the latest iteration of the open-source Verilog-to-Routing tool chain, a crucial platform for FPGA architecture research.
• Heterogeneous Fabric Support: The primary innovation is the enhanced capability to model and explore architectures classified as "Fabric and Beyond," supporting complex heterogeneous systems, integrated hard blocks, and specialized reconfigurable units.
• Improved Scalability and Performance: The tool chain features updates to core CAD algorithms (packing, placement, routing) to handle larger design sizes and significantly increase the speed of architectural exploration studies.
• Open-Source Access: Continuing the VTR tradition, the entire CAD flow remains open-source, democratizing access to state-of-the-art reconfigurable hardware research tools.

Technical Details

• Architecture Description Language (ADL) Enhancements: VTR 9 includes an updated ADL (likely XML-based) that permits finer-grained definitions of complex routing networks, hierarchical structures, and integration interfaces for diverse hard intellectual property (IP) blocks (e.g., DSPs, specialized memories, high-speed interfaces).
• Advanced Routing and Placement: Introduction of new algorithms optimized for managing resource contention and congestion inherent in heterogeneous fabrics, ensuring better Quality of Results (QoR) compared to previous versions.
• System Integration Flow: The tool provides standardized hooks and improved support for linking external synthesis tools and integrating with higher-level system modeling frameworks.
• Design Space Exploration (DSE): Enhanced features support automated parameterized architectural sweeps, allowing researchers to efficiently analyze the power, performance, and area (PPA) trade-offs across thousands of potential fabric configurations.

Implications

• Advancing RISC-V Integration: VTR 9 directly aids the RISC-V ecosystem by providing an accessible, rigorous platform for co-designing specialized compute fabrics that can be tightly coupled with open-source RISC-V cores. Researchers can explore optimized accelerators and custom instruction set extensions within a reconfigurable context.
• Democratization of Hardware Design: By offering a high-quality, open-source alternative to proprietary vendor tools, VTR 9 enables smaller teams, startups, and academic institutions worldwide to innovate in custom reconfigurable hardware architecture without high licensing barriers.
• Accelerating Domain-Specific Architectures (DSAs): The enhanced support for complex fabrics facilitates the rapid prototyping and optimization of architectures targeting specific domains, such as AI/ML inference or high-performance computing, driving innovation in next-generation silicon.
• Standardization of Research: VTR 9 further solidifies VTR's role as the de facto standard benchmark platform for evaluating new FPGA CAD algorithms, ensuring that research results are reproducible and comparable across the global research community.