Higher data rates, runtime recalibration, priority messaging, and advanced transport features boost performance but add verification complexity.
By Ujjwal Negi and Prashant Dixit
The Universal Chiplet Interconnect Express (UCIe) standard is redefining multi-die integration, enabling high-performance, scalable connections between heterogeneous chiplets. UCIe 2.0 introduced a dedicated manageability layer — a control plane for configuring, monitoring, and coordinating chiplet management elements independently from mainband and sideband data paths.
UCIe 3.0 builds on this foundation with higher data rates, runtime recalibration, priority messaging, and advanced transport features—boosting performance but adding verification complexity. Validating both the manageability layer and its interaction with these new capabilities requires a flexible, protocol-aware verification approach.
This article outlines the verification challenges in UCIe manageability, the impact of 3.0 advancements, and how the Questa One Avery UCIe Verification IP (VIP) addresses them.
The UCIe manageability layer is a dedicated control plane for configuring, monitoring, and coordinating management elements across chiplets in a multi-die system. Operating independently from mainband (application) and sideband (auxiliary) data paths, it ensures that system control and monitoring remain active regardless of data traffic state.
Fig. 1: System in package that supports manageability.
Management protocol defines control message semantics (e.g., UMAP, UDA) and packetizes them into MTPs for delivery between elements. Encapsulation is supported over mainband (management FLIT) and sideband (management port messages).
Fig. 2: UCIe manageability protocol hierarchy.
Verifying UCIe’s manageability layer is far from straightforward. Chiplets can host multiple management elements and ports, forming topologies that range from simple point-to-point links to complex multi-hop meshes. Verification must ensure accurate instantiation, configuration, and tracking across all connections. The discovery and initialization process adds further complexity—each management element must be identified, assigned a unique chiplet ID, and configured correctly, whether through front door or backdoor initialization flows.
Once the network is established, verification must validate routing and network ID mapping to ensure MTPs reach their destinations correctly, including handling multi-hop route-through paths, runtime updates, fallback mechanisms, and loop prevention. Transmitter and receiver behaviors—such as segmentation, interleaving, flow control, decapsulation, reassembly, and out-of-order handling—must be tested across multiple ports and encapsulation modes. Finally, protocol diversity introduces another challenge, as the transport layer may carry different management protocols (e.g., UMAP, UDA), all of which must be decoded, interpreted, and validated for compliance.
UCIe 3.0 raises the bar with several new capabilities.
| Feature | Challenge |
| 48/64 GT/s Data Rates | Testing links with tighter timing margins, more demanding equalization, and resilience under jitter and skew. |
| Runtime Link Recalibration | Mid-traffic validation of lane synchronization, state preservation, and recovery without data loss. |
| Priority Sideband Packets (PSTP) | Validating pre-negotiation priority sideband transfers, ensuring correct chaining, ordering of priority traffic, and seamless recovery after interrupting normal traffic. |
| L2 Sideband Power Down (L2SPD) | Testing low-power entry and exit sequences for sideband logic, with strict trigger timing and full functional recovery on wake-up. |
| Circular Buffer MTP Transport | Validating smooth buffer wraparound, avoiding overflows/underflows, and blocking illegal access. |
As UCIe adoption accelerates, verification must scale to handle complex manageability topologies and evolving features. The Questa One Avery UCIe VIP combines a modular, class-based architecture with targeted test capabilities, enabling accurate modeling of manageability domains while fully supporting verification of UCIe 3.0’s advanced high-speed and power-aware features.
The Avery UCIe VIP implements a flexible, modular architecture to model manageability domains across any system topology. Its configurable topology modeling allows users to define simple point-to-point connections or large-scale multi-chiplet networks, attach multiple management elements to a chiplet, and assign discovery roles for realistic system behavior.
Fig. 3: Multi-chiplet management domain.
For discovery and initialization, Avery VIP supports both built-in flows and user-defined sequences—with the ability to configure management ports and capability structures through front door protocol transactions or backdoor register access. A dedicated routing logic module builds and updates routing tables during discovery, validating reachability, detecting routing issues, and flagging integrity problems early.
Protocol-aware debugging adds full traceability from the management protocol layer to the physical link using MTP and MPG trackers, simplifying root-cause analysis. The built-in Questa One Test-suite Configurator further streamlines development by generating targeted compliance suites based on DUT type, relevant protocol sections, and enabled features, minimizing manual effort while aligning coverage with the UCIe specification.
Fig. 4: MTP association across trackers.
To address UCIe 3.0’s performance and power enhancements, Avery VIP includes dedicated test capabilities for key features.
For runtime link recalibration, it injects recalibration events during active traffic, verifying uninterrupted data transfer and correct equalization tuning. High-speed operation at 48/64 GT/s is stress-tested with compliance scenarios that push link training, equalization, and timing under conditions of high jitter and skew.
Priority sideband packet handling is validated through scenarios that test priority sideband packets (PSTP) pre-negotiation, mid-traffic interruption, chaining, and seamless resumption with full protocol compliance. Low-power behavior via L2 sideband power down is verified by API-triggered entry and exit tests, ensuring strict timing compliance and minimal detection logic activity during power-down.
Fig. 5: Interruption of normal sideband packet by PSTP.
The circular buffer transport feature is validated for legal and illegal state transitions, wraparound behavior, buffer reset handling, and protection against unauthorized access.
As UCIe evolves, verification environments must keep pace with increasing speed, complexity, and manageability scope. The Questa One Avery UCIe VIP delivers a comprehensive, scalable framework covering both UCIe 2.0 manageability and UCIe 3.0 enhancements to ensure functional correctness, compliance, and robust performance in next generation chiplet systems.
For a complete breakdown of the Avery UCIe VIP verification methodology and test suite structure, along with real-world deployment results, download the full whitepaper: Verifying the Evolving UCIe Landscape: A 3.0-Aware Architecture for Manageability and Beyond.
Prashant Dixit is currently working on the development of verification solutions for UCIe-based designs at Siemens EDA. With a strong background in the storage domain, he also manages the Storage Verification IPs team, focusing on the development and testing of NVMe and NVMe over Fabrics testing solutions. Prior to his role at Siemens EDA, Dixit contributed to the design and verification of IP and SoCs in the networking and storage domains at Samsung. Dixit earned a Bachelor of Technology in Electronics and Communication from Uttar Pradesh Technical University in 2004 and a Master of Engineering degree in Microelectronics from BITS Pilani in 2006.
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