LaZagna: An Open-Source Framework for Flexible 3D FPGA Architectural Exploration

TL;DR

LaZagna is an open-source framework enabling automated design, evaluation, and exploration of 3D FPGA architectures with customizable features and practical constraints, broadening research capabilities beyond prior simulation-only approaches.

Contribution

It introduces the first comprehensive open-source tool for 3D FPGA architecture generation, supporting high-level specification, RTL synthesis, and physical design, with new customizable interconnects and heterogeneity.

Findings

Successfully generated synthesizable RTL and bitstreams for 3D FPGA designs.

Conducted case studies demonstrating impact of architectural parameters on performance.

Showcases scalability and flexibility for future 3D FPGA research.

Abstract

While 3D IC technology has been extensively explored for ASICs, their application to FPGAs remains limited. Existing studies on 3D FPGAs are often constrained to fixed prototypes, narrow architectural templates, and simulation-only evaluations. In this work, we present LaZagna, the first open-source framework for automated, end-to-end 3D FPGA architecture generation and evaluation. LaZagna supports high-level architectural specification, synthesizable RTL generation, and bitstream production, enabling comprehensive validation of 3D FPGA designs beyond simulation. It significantly broadens the design space compared to prior work by introducing customizable vertical interconnect patterns, novel 3D switch block designs, and support for heterogeneous logic layers. The framework also incorporates practical design constraints such as inter-layer via density and vertical interconnect delay. We demonstrate the capabilities of LaZagna by generating synthesizable RTL that can be taken through full physical design flows for fabric generation, along with functionally correct bitstreams. Furthermore, we conduct five case studies that explore various architectural parameters and evaluate their impact on wirelength, critical path delay, and routing runtime. These studies showcase the framework's scalability, flexibility, and effectiveness in guiding future 3D FPGA architectural and packaging decisions. LaZagna is fully open-source and available on GitHub.