Lane Margining in PCIe Research
An interactive exploration of receiver margining capabilities in high-speed interconnects. Understand how signal integrity is validated without external equipment using the PCIe Gen 4+ specification.
The “Eye” Concept
In high-speed serial data (like PCIe), signal quality is visualized as an “Eye Diagram”. Lane margining measures the width (Time) and height (Voltage) of the eye opening.
Instructions: Use the sliders to introduce “Noise” (Voltage interference) and “Jitter” (Timing instability) to see how the eye closes and margins decrease.
The Margining Mechanism
How the PCIe controller communicates with the receiver to perform the test without external probes.
Setup
Enter Margining Mode via Control Registers.
Adjust
Step offset (time/voltage) until error.
Log
Record max offset before failure.
Restore
Clear offsets, return to mission mode.
Select a step above to see technical details.
The lane margining state machine requires precise handshake coordination between the Downstream Port (DSP) and the Upstream Port (USP).
Data Analysis: x16 Link Test
Results from a 16.0 GT/s (Gen 4) compliance test.
Pass Mask: > 20mV / > 0.2 UI
Lane Status Map (x16)
Click a lane to view specific margin registers.
Lane 0 Details
Margin Distribution Dataset: Run_2024_A
Research Findings
Lane 12 Anomaly
Consistently shows 15% lower voltage margin than adjacent lanes. Potential cause: crosstalk from power supply connector proximity on the test board.
Gen 4 Compliance
15/16 lanes meet the 20mV minimum receiver mask. The margining tool successfully predicted Bit Error Rate (BER) degradation before link failure.