The Universal Chiplet Interconnect Express (UCIe) specification is designed to foster a disaggregated die architecture ecosystem, prioritizing interoperability across devices with varying performance. To achieve this, the specification defines compliance mechanisms.
Compliance Goals
UCIe compliance testing aims to validate the mainband supported features of a Device Under Test (DUT) against a reference UCIe implementation. Supporting compliance testing is optional but crucial for devices seeking to participate in the UCIe compliance program.
Compliance testing is essential for several reasons:
Interoperability: It validates that a Device Under Test (DUT) functions correctly with a known good reference UCIe implementation, ensuring compatibility across different devices.
Adherence to Standards: Compliance testing verifies that the mainband supported features of a device align with the UCIe specification.
Testing Layers
UCIe compliance testing involves independent checks at different layers:
- Protocol Layer Compliance: Testing compliance at the protocol layer.
- Adapter Compliance: Ensuring the D2D adapter meets specifications.
- PHY Compliance: Validating the physical layer’s adherence to the UCIe specification.
Test Setup
The compliance testing system includes
- Reference UCIe design (Golden Die): A known, good UCIe implementation across all layers.
- DUT: One or more Devices Under Test, validated for die sort/pre-bond requirements.
- Interconnect: A silicon bridge or interposer for Advanced Package configurations, or a standard package for Standard Package configurations, connecting the Golden Die with the DUT.
These compounds are integrated into a test package for compliance and interoperability assessments.
Role of Sideband
UCIe sideband is crucial in compliance testing, enabling compliance software to access registers from different UCIe components for test setup and status monitoring. UCIe sideband is expected to be operational without firmware initialization.
Hardware Capabilities for PHY Compliance
The UCIe specification outlines required hardware capabilities in the DUT for testing Physical Layer functionalities, including:
- Timing & Voltage Margining
- BER Measurement
- Lane-to-Lane skew measurement
- TX Equalization
Compliance Register Block
UCIe implementations supporting compliance testing must include the Compliance/Test Register Block.
Ensuring Interoperability
UCIe compliance is vital for ensuring interoperability in the chiplet ecosystem. The UCIe specification provides a detailed framework for compliance testing, covering various layers and hardware capabilities. Adherence to these guidelines will help drive the development of UCIe-compliant solutions, fostering a more open and interoperable chiplet ecosystem.
