Omelet: A Packaging-Aware Hierarchical Interconnect Simulator for 2.5D/3D Chiplet Architectures

Monolithic integration of SoCs is reaching practical and economic limits, motivating the transition to disaggregated chiplet-based 2.5D/3D systems. In these systems, system performance depends not only on microarchitecture, but is tightly coupled to integration decisions such as stacking, interposers, and bonding methods. These packaging decisions directly shape communication characteristics, including link latency, bandwidth, energy, and I/O density. At the same time, communication is no longer confined to a uniform on-chip network. Instead, data movement traverses multiple interconnect domains, including on-chip wires, lateral interposer links, and vertical die-to-die connections. Since each domain is implemented using different physical technologies, they exhibit distinct electrical and communication characteristics, naturally forming a hierarchical interconnect structure. However, existing simulators rely on packaging-agnostic, decoupled abstractions that fail to capture technology-specific link behavior and cross-layer interactions. This disconnect obscures integration-driven bottlenecks and limits accurate system-level design space exploration. We present Omelet, a packaging-aware hierarchical interconnect simulator for 2.5D/3D chiplet systems. The simulator integrates intra-chiplet networks (Network-on-Chip, NoC), interposer-level communication (Network-on-Interposer, NoI), and vertical tier-to-tier links (Network-on-Layer, NoL) within a unified cycle-level framework, with link parameters derived from electromagnetic extraction and compact SPICE models of advanced packaging interconnects. This unified hierarchy enables architects to evaluate how packaging technologies, network architectures, and chiplet organizations jointly influence latency, congestion, and bottleneck formation in multi-chiplet 2.5D/3D systems. Omelet, with documentation and examples, is publicly available on GitHub 11https://github.com/sharc-lab/Omelet.