Multi-lane Link Crosstalk Generation During Lane Testing
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Solution Overview
Problem
Current interconnect architectures in computing systems face challenges in meeting the increasing demand for higher performance and power efficiency, particularly in servers and mobile devices, as they struggle to handle the complexity of advanced computing configurations and data rates beyond traditional PCIe Gen4 speeds.
Innovation Solution
The introduction of specialized testing link states in the link training state machine allows for precise testing of individual lanes within a multi-lane link, enabling the generation of real near-end and far-end cross-talk, which is critical for validating the performance of high-speed interconnects like PCIe Gen5, by allowing lanes under test to enter specific states while others generate cross-talk, thereby facilitating more realistic margin testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional multi-lane link testing is performed without specialized testing states, then testing coverage is limited and cannot generate real cross-talk, but implementing specialized testing link states increases device complexity
Solution Approach 1:
The patent segments the multi-lane link into individual lanes, allowing each lane to be tested independently while others generate cross-talk. The link training state machine is segmented into specialized testing states that control specific lane behaviors, enabling precise measurement of each lane's performance under realistic cross-talk conditions without requiring all lanes to be fully operational during testing.
Solution Approach 2:
The patent introduces an intermediary testing mechanism where non-tested lanes act as cross-talk generators through specialized testing states. These intermediary lanes produce controlled cross-talk signals that simulate real-world conditions, allowing the tested lane to be evaluated accurately without requiring full system operation. This intermediary approach bridges the gap between isolated lane testing and full-system testing.
2Ease of manufacture
If all lanes are tested simultaneously in traditional methods, then testing is simpler to implement, but cross-talk generation is insufficient and does not reflect real operating conditions
Solution Approach 1:
The patent makes the link training state machine dynamic by introducing state transitions that adapt lane configurations based on testing requirements. During specialized testing states, the system dynamically configures some lanes to transmit test patterns while placing other lanes in idle or cross-talk generation modes. This dynamic reconfiguration allows the same physical link to be used for both normal operation and realistic cross-talk testing without permanent hardware modifications.
3Speed
If high-speed interconnects operate at increased data rates, then performance improves, but susceptibility to cross-talk and signal integrity issues increases
Solution Approach 1:
The patent converts the harmful effect of cross-talk into a beneficial testing tool by intentionally generating controlled cross-talk signals through specialized testing states. Non-tested lanes are configured to transmit patterns that create realistic cross-talk conditions on the tested lane. This approach transforms cross-talk from an unavoidable interference into a controllable test parameter, allowing engineers to measure and validate system performance under defined cross-talk levels, thereby ensuring reliability at high data rates.
Data Source
AI summary
A port of a computing device includes multiple receiver-transmitter pairs, each of the receiver-transmitter pairs including a respective receiver and a respective transmitter. The device further includes state machine logic that detects a training sequence received by a particular one of the receiver-transmitter pairs on a particular lane from a tester device. The training sequence includes a value to indicate a test of the particular receiver-transmitter pair by the tester device. The particular receiver-transmitter pair enters a first link state in association with the test and one or more other receiver-transmitter pairs of the port enter a second link state different from the first link state in association with the test to cause crosstalk to be generated on the particular lane during the test.